Information
about the Valvetrain, Camshaft and Exhaust Header Pipe
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Information About Engine Valves -
I get so many people who tell me that when they have a problem with their engine, they cleaned and rebuilt the carburetor, but the engine would still run the same. So they remove the carburetor, clean it again, and the engine still acts the same. So they check the carburetor again! They say they checked it, cleaned it about 10 times. (Whew) Then they move on to the ignition system, but it checks out okay, too. Anyway, I tell them if you checked and cleaned the carburetor that many times and everything looked okay with it, then the problem obviously ISN'T in the carburetor or the ignition! There are other things that help make an engine run, such as the valves. I tell them to check the valve clearances, or the engine may need a professional valve job performed. Also, check for loose valve seats. The valves are the hardest working parts in any 4-cycle engine. They need attention, too. And so many people are ignorant or know nothing about the valves, how they work or their purpose.
The valve face will more than the seat because the moving part
always wears more than the stationary part. And main thing that cause valve
face wear on the exhaust valve is a worn guide, which cause the face to scrape
against the seat upon closing, and/or carbon deposits being lodged between
the face and seat. The intake valve face wears from guide wear also and/or
either lack of an air filter or not frequently using a new air filter. Clogged
filters can cause microscopic dust particles to penetrate the filter and
enter the combustion chamber.
If a 4-cycle engine cranks over too easy and is hard to start, and when it (or if) does start, it loses power and/or dies for no apparent reason after running for a while, then chances are the problem is in the valves. Valve faces and/or seats become worn after many years of use, and this lessons the clearance between the valve stems and lifters, or valve stems and rocker arms. Metal contracts (shrinks) when cold and expands (swells) when hot. Knowing this, when an engine gets hot, the valves swell, especially the exhaust valve, and this lessons the clearance between the stems and lifters. The hotter a valve gets, the less clearance it will have. When there's inadequate clearance, the valves won't close all the way, or stay closed long enough to seal in sufficient compression within the combustion chamber, the engine will lose compression, making the engine hard to start and when it does start, it won't produce much power. Sometimes gas will blow out the carburetor when the engine is revved up, too. And when the engine dies for no apparent reason, it'll be almost impossible to restart when hot. To fix this, a professional valve job will need to be performed. What causes valve faces and/or seats to wear is lack of an air filter element (which will wear parts within the entire combustion chamber under dusty conditions), a dirty air filter, a defective air filter, or an air filter that has not been changed in a long time. Air filtration is very important with any engine. Especially under extreme dusty conditions. And just like fuel filters, air filters can only filter out dust particles so small. The smallest pieces of dust penetrates the microscopic holes in the filter material, and wears parts within the combustion chamber.
Just cleaning the valves, setting the clearances to specs and "lapping them in" is not performing a professional valve job. If the engine lacks power or dies frequently, then chances are, the valves (and seats) aren't burnt, they're just warped from normal engine heat. This happens on seasoned flathead engine blocks and OHV cylinder heads for the first time. And chances are, the valve faces are worn too, due to normal wear against the seats. This is what causes insufficient valve clearance. Regrounding the valve faces at a 30° or 45° angle places the valve head in perfect alignment (perpendicular) with the stem or "straightens them out" again so they'll be good as new. And regrounding or recutting the seats at a 31° or 46° angle insures that the valve stems will be centered in the guides and the faces will seal 360° around. The reason for the 30°/31° or 45°/46° angles are so the valves and seats can wear into each other, producing a perfect 45-½° angle for each. Anyway, after the valves and seats are reground, the valve clearances can be set at .010" each with the piston positioned exactly at top dead center on the compression stroke. And then lap them in so the faces will produce a wear pattern on the seats (the lapping process helps produce the perfect 45-½° angle for each). After the valves are matched perfectly with the seats after about 2 hours of normal engine operation, the engine should start quicker, produce more power and the valves should last the life of the engine.
| A worn throttle shaft will also cause wear on the valve faces and seats. It's the #1 cause of most engines wearing out prematurely. If a carburetor has a worn throttle shaft, this will create a vacuum leak and the engine will idle poorly, if at all at times. Not to mention the engine will also draw in dirty air, causing wear on the valve faces/seats and piston rings, and engine will burn oil. More than .010" of play is considered too much for throttle shaft wear. Plus, at operating running speeds (3,600 rpm), the extra air will cause the engine to run lean on fuel, which will overheat the combustion chamber and cause the cylinder head to warp (blow a head gasket) and the piston and rings to wear prematurely, eventually resulting in severe engine wear and excessive oil burning. Along with regular maintenance, repair of a worn throttle shaft is required to help an engine last a long time. The most accurate way to check for amount of wear is to use a dial indicator. |
By the way - I get a lot of engines in my shop that need a valve job performed. Many other small engine repair shops will ignore the valves (or they're not trained to perform professional valve jobs) and assume the hard-starting problem is elsewhere with the engine.
If they're not burnt, then chances are, the valves and seats become warped from the block being heated under normal use after it was new and the metal "takes shape." Aluminum blocks (and heads) are worse than cast iron blocks (and heads). This happens with small engines as well as automotive engines. The block will actually deform a few thousands of an inch, moving the valves off the seats slightly, causing them to leak. Sometimes the cylinder wall(s) will deform a few thousands of an inch, too. Once the "seasoned" block or head takes shape, they won't warp any more. If the valves are leaking, then the valves and seats will need to be recut or reground so they're be in perfect alignment with each other and perpendicular with the guides.
To test for leaking valves, with the cylinder head removed and the piston at TDC on the compression stroke and both valves fully closed, spray WD-40 or an equivalent light liquid around each valve and then apply compressed air with a rag wrapped around the air nozzle through the exhaust and intake ports. Be sure to place the nozzle with the rag snug against the ports so full pressure will be against the valves. If bubbles form around the valves when applying the air pressure, this means the valves are leaking and a professional valve job is required.
Just cleaning the valves and
lapping them in, and then assume the engine will run fine for many years
without problems is definitely not how a professional valve job is performed.
Valve lapping compound is not meant for "grinding valves". I know that it
says on the label "Valve Grinding Compound," but this is wrong because
it doesn't grind valves (or seats) whatsoever. It's actually used to put
a rough surface on both the valve face and seat so they'll wear into each
other, forming a perfect seal to keep the valves from leaking compression.
Remember, when/if you have a
repair shop perform a valve job, be sure to ask them how it's done. In other
words, test their knowledge. If they say that the valves be removed, cleaned
up, lapped in and then set the clearance, this is not the correct way to
do it. Due to normal engine heat and "twisting" of the engine block (which
is normal and happens to all flathead engines and OHV cylinder heads), valve
heads become warped. New engine blocks (or cylinder head on OHV engines)
rather it be cast iron or aluminum, will sometimes become "distorted" (bend
and twist) a few thousands of an inch when it gets hot from normal use. The
valves will become warped to match the warped block (or head). Therefore,
to prevent loss of valuable compression and engine power, the valve faces
will need to be reground in a valve grinding machine and the seats recut
or reground with a valve seat cutter or grinder to put everything back in
correct alignment. The head will literally move a few thousands of an inch
offcenter of the valve stem. Therefore, the valve faces must be reground
in a valve grinding machine, or if a valve is severely burnt, it should be
replaced. And again, due to normal engine heat, the valve seats will literally
move a few thousands of an inch offcenter of the valve guide. Therefore,
the seats must be reground with a seat grinder or cutter so the valve faces
will seal 360° around the seats.
Valves can leak! For example, if fuel sprays out of the carburetor on a twin cylinder engine when it's running at fast speed, then the following causes are...
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The hole in the main jet of the carburetor was mistakenly enlarged when cleaning
because it was clogged with debris.
- Solution: Install the correct size main jet or another known good carburetor.
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Inadequate valve to lifter clearance. The intake valves will not close in
time to trap the air/fuel mixture in the combustion chamber, blowing some
of it back through the carburetor. This happens a lot on twin cylinder engines
as the valve faces wear into the seats.
- Solution: A professional valve job needs to be performed. And then set the valves at .008" for the intake and .010" for the exhaust.
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But if an intake valve isn't moving, then chances are, a lobe on the camshaft
is wore down. This happens when water gets in the crankcase and over time
condensation attaches itself to the lifter, rusting it. While the engine
is running, the rusted lifter wears the lobe until it's wore down or "rounded."
This sort of thing will also prevent a single cylinder engine from revving
up.
- Solution: Install a good, unworn camshaft and good , unworn lifters.
About Lead In Gas -
Lead in gas was actually meant for older automotive engines (pre-1970) because they had soft cast iron valve seats. The cylinder heads were made of cast iron and the seats were cut or ground directly in the head with no inserts. These seats was not heat-treated and would wear when no lead is present in gas. However, the later model automobile engine valve seats (1971-present) are heat-treated and last a lot longer. The seats were still cut or ground in the [cast iron] heads, but are heat-treated. The aluminum automotive heads have heat-treated steel inserts for valve seats. And virtually ALL small engine valve seats come from the factory heat-treated. They are steel inserts, and rarely wear when no lead is present in gas.
How to Perform a Professional Valve Job - Top of page
First of all, to gain more power
and torque from virtually any flathead single or twin cylinder engine, perform
a professional valve job and the valve clearances will need to be increased.
Resurface the cylinder heads on a flat sanding disc to insure proper head
gasket sealing. Nothing else may be needed to be done to the engine, except
for perhaps a professional tune up. Many twin cylinder engines have inadequate
valve clearances and this robs the engine of proper operation and valuable
power. Perform a professional valve job, and set the clearances (between
the valve stems and lifters) at .010" for the intake and .014" for the exhaust.
After increasing the valve clearances, the engine will start quicker, idle
better and produce more power at low and high rpm.
Four tools are required to perform a valve job: valve spring compressor, valve grinding machine, valve seat grinder or cutter and valve lapping compound and valve lapping (spinning) tool. To do a lousy valve job, some people will just remove the valves, clean them thoroughly and then use valve lapping compound to reseal them to the seats and then reset the valve clearances. Doing this will help an engine to run better for a while, but it's not how to perform a professional valve job. To do it right the first time and make the valves last a longer so the engine will produce power...
- First rotate the crankshaft until the piston is at top dead center (TDC) on the compression stroke. Or, rotate the camshaft (if the crank is out of the block) until both valves are fully closed. If it's a twin cylinder engine, do this for each cylinder.
- After removing the crankcase breather, remove the valves using a valve spring compressor tool. Be sure not to lose the keepers! Store the valve components in a container so nothing will be misplaced! If you don't have a valve spring compressor tool, two medium size flat screwdrivers can be used to compress the spring and then have someone else remove and install the keepers. I had to do this when I first started working on engines. Then I found that a valve spring compressor makes it a lot easier.
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Remove
the valves, clean all the parts, and use a wire wheel to clean the carbon
from the valves. They may need to be sandblasted if the carbon is really
hard to remove.
- Inspect the valve face for wear, and measure the stem diameter for wear.
- Check the valve guides for wear. Most of the time, the exhaust guide will wear more than the intake due to carbon deposits. The maximum wear limit on the 7hp and 8hp Kohler engines is .005" for the intake,.007" for the exhaust. And on the 10hp, 12hp, 14hp and 16hp Kohler engines, it's .006" for the intake and .008" for the exhaust. If the guides are worn, install new guides or have a new thin-wall bronze liner installed. An excessively worn intake and/or exhaust valve guide will cause an engine to make a popping sound out the intake or exhaust while it is running.
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If they're not burnt, bent or badly warped, then used valves can be refaced
on a valve grinding machine at an automotive engine machine shop. But if
they're damaged or excessively worn in any way, they must be replaced. If
the valves are reusable, grind the intake and exhaust valve(s) and seat(s)
at 45º/46º angles (Kohler engines), respectively. The reason there's
a 1º difference is because as the valve and seat wear together, they'll
form a perfect 31-½° angle (intake, for high performance use) or
45-½° angle (intake and exhaust) leak-proof seal. As the valves/seats
break-in, the engine will produce slightly more power because they'll be
retaining full compression within the combustion chamber. In an average engine,
it takes about 2 hours of operation for the valves to fully seat. When
dyno-testing an engine, make sure it has at least 2 hours of break-in time
on it.
NOTE: All of Kohler's valves come from the factory with a 45º angle, and the seats are ground at 46º. And there's no need for the valve seat contact area to be in the center of the face of the valve. (This is determined by lapping in the valves.) The engine will actually breath better at higher rpm if the seat contact area is towards the edge of the valve face. -
After grinding the valves and seats, and with the governor assembly, lifters,
camshaft, crankshaft, piston/rod and bearing plate all properly installed,
and with the piston at TDC on the compression stroke (this when the base
circle of the cam lobes are on top and both valves are fully closed), install
the valves, springs, retainers and keepers and then check for proper valve
lash (the clearance or gap between the valve stem and lifter). Set the valve
clearances as follows for Kohler's K-series and Magnum single cylinder engines:
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Always set the valve clearance
when an engine is cold. Because metal expands when hot and shrinks when cold.
On a fresh valve job, set the clearance on the maximum specs to allow for
the valve face and seat to wear into each other. And then after approximately
25 hours of running time, recheck the clearances and set them at on the minimum.
(If the gap haven't already minimized.)
- For the 7hp and 8hp engines, the clearances are: .006"-.008" for the intake and .017"- .019" for the exhaust. Adjustment is made by lightly grinding the end of the valve stems. Be careful not to grind too much! This is the same way Briggs & Stratton and Tecumseh flathead engines valves are adjusted.
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Use steel feeler
gauges to set the valve clearances. For the 10-16hp engines, for ordinary
yard use, the valve clearances are: .008"-.010" for the intake and .017"-.019"
for the exhaust with the piston at TDC on the compression stroke. This is
when both valves are fully closed. For competitive pulling, set the valve
clearances at .010" for the intake and .014" for the exhaust.
-
- When checking the valve lash on any engine, the piston in the cylinder for the valves that you're checking (on multiple cylinder engines) must be at top dead center (TDC) on the compression stroke. This places the lifters on the base circle of the cam lobes. The reason there's a valve lash is so the valves can fully close, sealing in the compressed air/fuel mixture in the combustion chamber. Too little lash, and some of the compression will escape through one or both valves, and in over time, a valve may burn. Too much lash, and the valves won't open fully, preventing the engine from producing full power.
- To adjust the valves, remove the valve cover, and then rotate the crankshaft by hand until both valves are fully closed with the piston at TDC on the compression stroke. If one valve opens slightly and the other closes slightly and vice-versa while rotating the crankshaft back and forth, then the piston is on the exhaust stroke and the crankshaft needs to be rotated one full turn (180°). This will guarantee that both valves are fully closed so accurate valve adjustments can be made.
- Valve adjustment is made with the engine cold, with a flat feeler gauge and on the 10-16hp engines, with the lifter held in place with a slender 1/2" open-end wrench and turning the adjuster screw in the lifter with a 7/16" open-end wrench. When checking valve clearance, always have the piston at the TDC position on the compression stroke. And make sure the ends of the lifters and valve stems are ground square for proper adjustment.
-
After making the proper lash adjustments, remove the valves, and apply a
small quantity of valve lapping compound (available at most auto parts stores)
on each valve face and then
use
a valve lapping tool (also available at most auto parts stores) to lap the
valves in the seats (rotate each valve back and forth with the tool) until
the "grinding sound" goes away. This process is important. It seals the valves
in the seats.
-
After lapping in the valves, remove the valves
and thoroughly clean the compound material from the valves and seats and
then inspect the valve faces to see if the compound made full contact of
360º around each valve face and seat. If it didn't, then the valve is
warped, or the face or seat wasn't ground correctly and will need to be re-done.
- When installing the valves, lubricate the stems with motor oil. After compressing a valve spring, apply a small quantity of grease (chassis lub) on each keeper and on the end of a flat screwdriver, and then place the keeper on the screwdriver and use the screwdriver to place the keeper on the stem. (The grease will hold the keepers to the stem until the spring can be released.)
- Rotate the crankshaft and observe the opening and closing of each valve. And take notice that the springs don't coil-bind. (Coil-bind is when the coils of the spring actually touch each other when the cam is at full lift. This may happen only with a high-lift cam.) If the springs do coil-bind, it may be necessary to remove the springs and grind some of the end off of each spring or acquire a different set of springs.
- Reinstall the crankcase breather using new gaskets, and that's it! Return To Previous Web Page.
NOTE: Valve rotators rotates the valves slightly as they open to clean or "wipe" away any carbon deposits from the valve face and seat to prevent the valve from burning. Shorter valve springs must be used with rotators to prevent coil bind at full valve lift. And rotators can be used in any 10hp-16hp Kohler engine. They help the valves last longer.
How to Perform a Professional Valve Job on a Twin Cylinder Flathead B&S or Kohler engine -
To gain more power and torque from virtually any flathead two or twin cylinder engine, perform a professional valve job and the valve clearances will need to be increased. Resurface the cylinder heads on a flat sanding disc to insure proper head gasket sealing. Nothing else may be needed to be done to the engine, except for perhaps a professional tune up. Many twin cylinder engines have inadequate valve clearances and this robs the engine of proper operation and valuable power. Perform a professional valve job, and set the clearances (between the valve stems and lifters) at .010" for the intake and .014" for the exhaust. After increasing the valve clearances, the engine will start quicker, idle better and produce more power at low and high rpm. To perform a professional valve job on a twin cylinder flathead B&S or Kohler engine, the parts that will be needed are: two head gaskets, two crankcase breather gaskets, intake manifold mounting gaskets and valve stem seals (for intake valves only). New valve guides, especially for the exhaust valves, may also be needed. But that's to be determined once the valves are removed. A quality-made valve spring compressor tool is required to remove and reinstall the valves. The valve faces and valve seats angles are to be reground or recut at 45° (intake valve face for Kohler), 30° (intake valve face for B&S) and 46° (intake and exhaust seats for Kohler and exhaust seat only for B&S), 31° (intake seat for B&S), respectively. If you can't do this yourself, a local automotive machine shop can do it for you. You'll need to take the engine or tractor to the shop to have the valve seats reground or recut. Make sure they're reground or recut at the proper angle, too! And it'll be a good idea to have both cylinder heads resurfaced on a flat sanding disc to ensure proper head gasket sealing. The head bolts can be reused. They rarely go bad. |
If you need any of the parts listed below, please contact
A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia,
MO 65203-9136 USA |  Phone:
1-573-875-4033. Please call Monday-Friday, 9am to 5pm, Central time. If no
answer, please try again later. (When speaking with Brian, please be patient
because I stutter.)  Fax:
1-573-449-7347.  E-mail:
pullingtractor@aol.com. You can
also contact us through Yahoo! Messenger:
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 New Valves for
Kohler engine models KT90/KT91. These valves not available in
aftermarket. 
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Intake and Exhaust
Valves for Kohler K-series and Magnum models K141 (6¼hp), K160 (6.6hp),
K161 (7hp) and K181/M8 (8hp) flathead cast iron block engines.
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Intake and Exhaust
Valves for Kohler K-series and Magnum models K241/M10 (10hp), K301/M12 (12hp),
K321/M14 (14hp) and K341/M16 (16hp) flathead cast iron block engines.
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New Valves for
Kohler K-series K361 (18hp OHV) cast iron block engine. These valves
not available in aftermarket.
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New Valves for
Kohler twin cylinder flathead engine models KT17, KT17II, KT19, KT19II and
KT21. These valves not available in aftermarket. NOTE: Valve seat
must be recut or reground to either 31° or 46° to
match face angle on new valve.
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New Valves for
Kohler twin cylinder flathead engine models MV16, M18, MV18, M20 and MV20.
NOTE: Valve seat must be recut or reground to either 31° or
46° to match face angle on new valve.
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| è Valves for other makes and models of small engines are also available. NOTE: Valves for Kohler twin cylinder flathead engine models M20 and MV20 are no longer available from Kohler. However, the aftermarket valves are back-ordered due to a tsunami, which wiped out several factories in China or Taiwan. They're rebuilding the factories now, but it'll be some time before they'll have valves (and other parts) available. | |||||
Stock (centered) Cast Iron Valve Guides. Note: After
installation, these guides may need to be reamed out with a 5/16" reamer
for proper valve stem clearance.
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  Valve Guide Removal and Installation Tool. Use with a big hammer
to drive out and install valve guides. $10.00 each, plus shipping
& handling.  |
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 Straight Flute High Speed Steel Precision Chucking Reamers.
Perfect size to ream out new valve guides to OEM Kohler specs or installing
Chevy valves in Kohler engines. Provides proper clearance. Will not allow
the valve stems to be too loose or too tight.
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 Valve Stem Seals
for Kohler engine model K361 (18hp OHV), and KT-series and Magnum flathead
twin cylinder engine models MV16, KT17, KT17II, KT19, KT19II, M18, MV18,
M20 and MV20. Comes with complete gasket sets for these engines. Dimensions:
5/16" i.d. (stem) x .500" i.d. (guide). Kohler part #'s 45 032 01-S, 52 032
13-S.
Valve Stem Seal for Kohler engine models CH18-CH25, CH620-CH730, CH740, CH750,
CV17-CV25, CV620-CV730, CV740, CV750. OEM Kohler part # 66 032 05-S.
$5.85 each, plus shipping & handling.
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 New 7° Valve
Spring Keepers for 5/16" diameter valve stems. Fits 6¼hp-16hp K-series
and Magnum cast iron block, 18hp/K361 OHV engines and twin cylinder KT series
and Magnum flathead engines. Also fits 6hp-18hp single and twin cylinder
Briggs & Stratton exhaust valves. Briggs & Stratton part # 494553;
Kohler part # 41 755 10-S.
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OEM Kohler Valve Spring Retainers and Rotators for 5/16" diameter
valve stems. Fits 6¼hp-16hp K-series and Magnum cast iron block, 18hp/K361
OHV engines and twin cylinder KT series and Magnum flathead engines. Also
fits 6hp-18hp single and twin cylinder Briggs & Stratton exhaust valves.
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 Crankcase Breather
Reed Valve for Kohler 10hp-16hp K-series and Magnum flatheads and 18hp OHV
engines. Prevents dust and dirt from entering crankcase and maintains crankcase
vacuum so engine will produce more power. OEM Kohler part # 235047-S.
$9.10 each, plus shipping & handling.
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 OEM Kohler Stock
Valve Springs for Kohler K-series and Magnum K241/M10 (10hp), K301/M12 (12hp),
K321/M14 (14hp), K341/M16 (16hp), K361 (18hp OHV), K482, K532 and K582 engines.
Good for up to 4,800 rpm. NOTE: Used OEM valve springs rarely lose
their pressure. They can be reused with a stock-lift cam as long as they're
not pitted with rust, which makes a weak spot and could cause the spring
to break over time.
New OEM Kohler Stock Valve Springs for Kohler KT-series and Magnum flathead twin cylinder engine models MV16, KT17, KT17II, KT19, KT19II, M18, MV18, M20 and MV20. OEM Kohler part # 25 089 01-S. $3.60 each, plus shipping & handling. |
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| Quality-Made, Heavy Duty, Scissors-Type Small Engine Valve
Spring Compressor. NOTE: Not designed to compress double valve springs.
$25.00 each, plus shipping & handling.
|
 Quality-Made, Heavy Duty,
C-Type Small Engine Valve Spring Compressor. NOTE: Not designed to compress
double valve springs. $35.00 each, plus shipping & handling. |
Quality-Made, Extreme Duty Valve
Spring Compressor. Easily compresses high-performance single and dual valve
springs for Kohler single cylinder pulling engines! Safe and easy to use.
$15.00 each, plus shipping & handling.
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| If you need something that's not listed here, please contact me and I'll see if I can get it for a reasonable price. Please contact me if you're interested in any of the above parts or items. | |||||
For Kohler K-series and Magnum
engine models K141 (6¼hp), K160 (6.6hp), K161 (7hp) and K181/M8 (8hp).
Dimensions: .310" i.d. x .5645" o.d. x 1.686" overall length. Kohler part
# 230007-S.
For K-series and Magnum engine
models K241/M10 (10hp), K301/M12 (12hp), K321/M14 (14hp), K341/M16 (16hp),
K482, K532 and K582. Dimensions: .310" i.d. x .629" o.d. x 2.135" overall
length. Kohler part # 235007-S.
For KT-series and Magnum flathead
twin cylinder Kohler and Magnum engine models MV16, KT17, KT17II, KT19, KT19II,
M18, MV18, M20 and MV20. Dimensions: .305 i.d. x 563" o.d. x .500" reduced
o.d. (for seal) x 1.378" overall length. Kohler part # 52 316 08-S.
Retainer (non-rotator type;
for intake valve). Requires 1-11/16" length valve spring (uncompressed height).
OEM Kohler part # 230011-S.
Rotator (scrapes carbon from
valve face and seat). Requires 1-9/16" length valve spring (uncompressed
height). Replaces Briggs and Stratton part # 691939; OEM Kohler part # 52
413 01-S.
Small Crankcase Breather
Filter. Prevents dust and dirt from entering crankcase. Fits various K-series
engine models K241 (10hp), K301 (12hp), K321 (14hp), K330/K331 (12½hp),
K341 (16hp) and K361 (18hp OHV). Fills about 1/3 area of breather plate.
Prevents dust and dirt from entering crankcase. OEM Kohler part # 235118-S.
$9.10 each, plus shipping & handling.
Large Crankcase Breather
Filter. Prevents dust and dirt from entering crankcase. Fits various K-series
10-16hp and all Magnum engine models M10 (10hp), M12 (12hp), M14 (14hp) and
M16 (16hp). Fills entire area inside of breather plate. OEM Kohler part #
47 050 01-S. $5.60 each, plus shipping & handling.
How to Repair a Loose Valve Seat in an Aluminum Flathead Block Engine - Top of page
Below is the professional
way of doing it.
- The valve will need to be removed from the block or head.
- The loose seat will need to be peened back in place with a 1/4" diameter blunt punch and medium size hammer or the ball end of a medium size ball-peen hammer. "Peening" is when the aluminum is "pounded" 360° around the seat so it will remain tight. Be sure to stagger the punches to begin with so the seat will be centered and won't sit crooked in the block or head.
- Perform a professional valve job by using a valve seat cutter and valve refacer to true up both the seat and valve face. Recut both seats and grind both valve faces, set the valve clearances to specs (to make sure the other valve seals good, too) and then lap the valves in so they'll seal perfectly upon break-in.
The reason a valve seat loosens in an aluminum engine block or cylinder head is because either the factory didn't press the metal tight enough around the seat or the aluminum expanded just enough with engine heat causing the seat to loosen. After the seat is securely tightened back in place, it shouldn't give any more trouble.
NOTE: Sometimes the seat can loosen so much, the counterbore where the seat rests will become enlarged. In fact, it can be too large to peen the seat back in place. When this happens, the counterbore will need to be bored for an oversized outside diameter seat. It takes a reputable machine shop/business to perform this type of repair.
How to Repair a Loose Valve Seat and Valve Guides in the K361 18hp OHV Cylinder Head - Top of page
The Kohler engine model K361
18hp single cylinder cast iron block OHV cylinder head is notorious for one
or both valve seats and/or one or both valve guides becoming loose. What
causes a seat to loosen is the aluminum was molded around the steel seats
with a "tongue and groove" design to secure the seat in place. Due to normal
(or perhaps excessive) engine heat, sometimes the two metals (aluminum head
and steel seat) will separate from each other, allowing the seat to loosen.
First of all, before attempting to repair a loose seat, if the valve guide for the seat in question is worn (inside diameter) or loose in it's bore, it will need to be repaired first.
- For the intake guide, if the guide is tight in its bore, but the inside is worn, a new guide can be installed. Use Loctite® Threadlocker Red 271™ or Permatex® Red Threadlocker to help secure the new guide in the head. The center hole may need to be reamed for proper stem to guide clearance. The Kohler part number for the intake guide is 45 016 02-S. The OEM exhaust guide is no longer available from Kohler. The part number for the exhaust guide is 45 016 04-S. If you're lucky, maybe one can be found in a dealer's old stock.
- Or instead of removing the guide and installing a new one, a thin-wall bronze sleeve can be installed in the guide to regain proper stem to guide clearance. This requires specialized tools and equipment. Most automotive engine machine shops can do this. Or install a new valve guide.
- But if either guide is loose in their bore, a cast iron or bronze guide slightly larger than 5/8" o.d. with a 5/16" i.d. hole that's made for another make and model of engine will need to be machined and installed. The bore for the guide in the head may need to be reamed to accept the oversize guide and be perpendicular with the centerline of the valve seat, then the center hole may need to be reduced for proper stem to guide clearance. Use Loctite® Threadlocker Red 271™ or Permatex® Red Threadlocker to help secure the guide in the head.
How to Repair a Loose Valve Seat:
- Acquire a quality steel valve seat insert with the outside diameter slightly larger than the counterbore of the old seat, but the same approximate inside diameter so the original size valve can be reused.
- With the head set up in a valve seat machine or on the table of a milling machine with the right kind of tooling, cut into the head to remove the old seat.
- Bore the counterbore for the new seat exactly .003" smaller than the outside diameter of the new seat for an interference fit and machine the depth of the counterbore the same height as the new seat.
- Knurl the circumference of the new seat in a metal lathe to help prevent it from loosening in the head.
- Chamfer or bevel the lower outer edge of the new seat in the metal lathe for easier installation into the counterbore.
- Apply Loctite® Threadlocker Red 271™ or Permatex® Red Threadlocker on the circumference of the seat and/or in the counterbore.
- Press or drive the new seat perpendicular into the counterbore until it bottoms out.
- The seat angle is then cut or ground to match the angle on the valve face and be perpendicular with the centerline of the valve guide.
About Installing Bigger Valves in the K361 (18hp) OHV Engine Cylinder Head -
On the K361's cylinder head, the stock valve head diameters are: intake - 1.438"; exhaust - 1.400". The exhaust valve is already plenty big enough, even for high rpms. But there's not that much room in the combustion chamber to install a bigger intake valve because a bigger seat would need to be installed first. The outside diameter of the seat is always larger than the diameter of the valve head. The biggest intake valve that can be installed would be about 1.5", which really wouldn't give the engine that much more performance. For more noticeable performance, the intake valve needs to be about 20% bigger than the exhaust valve, which would make it 1.68". And this is way too big for the K361 head.
Advertisement:
| If you need any of the parts or services listed below, please contact
A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia,
MO 65203-9136 USA | Phone:
1-573-875-4033. Please call Monday-Friday, 9am to 5pm, Central time. If no
answer, please try again later. (When speaking with Brian, please be patient
because I stutter.) Fax:
1-573-449-7347. E-mail:
pullingtractor@aol.com. You can
also contact us through Yahoo! Messenger:
|
 Cylinder head gasket for
K90/K91 (4hp) Kohler flathead engines. Approximately .050" compressed thickness;
included in complete engine rebuild gasket set. Kohler part # 220124-S.
|
 Cylinder head gasket for
K141 (6¼hp), K160 (6.6hp), K161 (7hp) and K181/M8 (8hp) Kohler K-series
and Magnum flathead engines. Approximately .050" compressed thickness; included
in complete engine rebuild gasket set. Kohler part # 41 041 10-S.
|
 Cylinder head gasket for
10hp, 12hp & 14hp K-series and Magnum flathead engines. Approximately
.050" compressed thickness; included in complete engine rebuild gasket set.
Kohler part # 47 041 15-S.
|
 Cylinder head gasket for
16hp K-series and Magnum flathead engines. Approximately .050" compressed
thickness; included in complete engine rebuild gasket set. Kohler part #
45 041 17-S.
|
 Cylinder head gasket for
18hp K361 K-series OHV engine. Approximately .050" compressed thickness;
included in complete engine rebuild gasket set. Kohler part # 45 052 02-S.
|
 Head gasket for MV16, KT17,
KT17II, KT19, KT19II, M18, MV18, M20 & MV20 twin cylinder flathead Kohler
engines. Kohler part # 52 041 20-S.
|
| Prices below are with the engine out of the engine, and on my work
table.
Other Services include:
|
Install oversize valves in
OEM [Kohler] block: $150.00 - $200.00 (depending size of valves)
labor, plus return shipping & handling. Price does not include any
parts.
Modifying the Stock Valves and Seats for Improved Performance -
First of all, part of what makes
an engine to produce power is the valves and the valve seats. They must form
a perfect seal so the air/fuel mixture will be trapped within the combustion
chamber on the compression stroke. If you're using or if rules require you
to use stock valves, more performance can be had by running the valves on
the edge of the face. Create a minimum .030" face width for intake and .060"
face width for exhaust. Enlarge the seats to match the valves and make them
the same width as the valve faces, which is .030" for the intake and .060"
for the exhaust. Reworking the valves and seats like this is like having
slightly larger valves. And lightening of the valve heads (make them lighter
in weight) will provide easier lifting and a faster closing response times,
to gain a few more rpm and more power. By grinding the intake valve head
thinner (grind away the underneath part) and giving it a 30º angle instead
of the factory 45º angle will allow the valve to be lighter in weight
even more. But leave the exhaust valve at the factory 45º angle, to
prevent it from becoming concaved (collapsed in the center) over time. Grind
the underneath of each valve close to the face-to-seat mating area, to improve
overall flow at full valve lift.
To perform a high-performance valve job, grind a 30º angle
on the face of the intake valve and a 31º angle on the seat. Lap the
valve(s) in their seats, and then cut away the metal next to the lapping
area and swirl-polish (smooth the metal) underneath the intake valve head
so more air/fuel will enter the combustion chamber. Because any restriction
of the incoming air through the intake opening won't allow an engine to produce
more power. The 30º angle plus the undercutting and swirl-polishing
will add approximately 15% more airflow at higher rpm, which equals to about
2-3 more horsepower to an engine that originally had a 45º angle on
the intake valve and seat. And for the exhaust gases to exit the combustion
chamber quickly, grind a 45º/46º angles respectively, and undercut
the exhaust valve head. Because any restriction of the exhaust opening will
cause an engine to lose power and possibly not allow it to rev to its full
potential at higher rpm.
To find the face-to-seat mating area, first enlarge and grind the seat angle and rework the valves as mentioned above. Then lap the valves in with valve lapping compound, to see where the contact area is. Now remove the metal from the underneath of the head until there is very little metal left next to the contact area. Swirl polishing the underneath of the intake valve head will help, too. This may also need to be done if "shaving" the stock cylinder head.
FYI - The way I swirl polish the underneath side of a valve head is I chuck the valve stem in our drill press, turn it on slow, and then I hold a 1" diameter stone in a die grinder (with the die grinder turned on) against the head until it has a somewhat swirled surface. Then I polish the surface with #40 emery cloth until it's smooth.
There are two ways to remove metal from the underneath of the valve head:
- Remove the metal from the underneath of the valve head in a metal lathe.
- Chuck the valve in a handheld electric drill, then hold the underneath side of the valve head at a 90° angle to a spinning bench grinding wheel while spinning the valve in the opposite direction. It grinds faster this way.
- Either way produces excellent results.
If an engine is going to turn above 4,000 rpm, stiffer valve springs will need to be installed along with heavy-duty retainers. (And definitely make sure the flywheel is precision balanced or better yet, install a steel flywheel... along with a quality connecting rod that has an inserted bearing.) Stiffer valve springs reduce the chance of "valve float," which occurs at high rpm. That's when an engine makes a "sputtering" sound and/or sprays fuel out the carburetor at high speed.
If one is lucky enough to find some, they could use the inner spring of a high performance automotive valve spring kit in a single cylinder engine. Stock keepers should work fine, too. To reduce the chance of valve float, use dual springs along with stainless steel valves, hardened retainers and keepers when using a steel cam that has a lot of lift (more than .460" of lift). If using ordinary valves with dual springs, the head of the valve(s) (especially the exhaust valve) might become concaved over time because of the extreme pressure. And make sure that "coil bind" doesn't occur (when the spring become totally collapsed and the coils actually touch each other) when the valve is at full lift. Coil bind could break a good cast camshaft or even bend a steel one.
A Stock Cam with Big Valves VS. a Big Cam with Stock Valves?
I think that by using a stock cam with big valves versus a big cam with stock valves wouldn't make that much difference in engine power. Because big valves will allow more airflow in the combustion chamber, plus the cylinder head would need to be machined for the bigger valve for clearance, BUT a stock cam is limited to it's lift and duration. And a big cam would allow the combustion to draw more air, plus the cylinder head would need to be machined for the extra valve lift, BUT the stock valves would limit the amount of airflow. So using one or the other wouldn't work as well as having both of them working together.
With all high performance cams that have lift of about .400" or more, the lifter bores (part of the engine block) needs to be ground down so the cam lobes can move the lifters up further so they'll clear the block.
Large base lifters are required for cams with a lift above .400". And extreme big tool steel lifters are required for cams with a lift above .572". Either of these lifters are available from Vogel Manufacturing Company (http://www.vogelmanufacturing.com).
Installing Bigger Valves in a Flathead Engine for Improved Performance -
In order for an engine to build up more compression and to gain more power and higher rpms, an engine needs to flow more air (and fuel) in and out of the combustion chamber. Therefore, the valves (and ports) needs to be approximately 22% - 40% bigger than the originals. In the 10hp and 12hp Kohler engines, the original OEM intake valve can be used in the exhaust hole. If you use your tractor ONLY for competitive pulling, an intake valve will hold up just fine in the exhaust hole. Don't worry about it burning. Most pulling tractors don't run long enough to burn valves. (In my personal experience, I've ran an intake valve in my 30ci since 1990 and it has held up just fine.) But if you plan to mow grass and do general yard work too, it'll be best to use a 16hp exhaust valve in the exhaust hole. All intake valves are made of mild steel. Exhaust valves are heat treated, to withstand prolong extreme exhaust heat.
On the 16hp engines, a special made or larger automotive valve must be used for both the intake and exhaust, as long as the stem diameter is the same or slightly larger. The valve guide will need to be reamed out to match the larger stem, too. The overall valve length for OEM stock Kohler valves is 4.635". If you have a longer valve that you want to install, the valve stem will need to be shortened and the keeper groove recut in a metal lathe. If using a valve with a larger diameter stem, it's best to narrow the stem diameter in the area that's under the valve head and above the valve guide (port area), which, depending on cam lift and duration, will give about 22% - 40% increase in air flow. Undercutting and swirl polishing underneath the valve heads will increase and smooth the air flow, too. Undercutting also lightens the valves so they'll be less strain on the valvetrain when the cam opens the valves.
On the intake valve side, for every 1/8" increase in diameter, about 1 horsepower is added for a 4,000 rpm limit engine and 2-3hp is added for a non-governed/high-performance wide open throttle engine. Of course, according to the diameter of the intake valve, the exhaust valve will need to be increased by 25%, to quickly rid the combustion chamber of the burnt gases. And the reason the intake valve is bigger than the exhaust is because air (and fuel) enters the combustion chamber under vacuum and exits under pressure. So there is no need to make the exhaust valve the same size as the intake valve.
The approximate oversize valves have been found to work well in the following most popular Kohler engines. These are for engines that run at wide open throttle. Stock engines that run at around 4,000 rpm can use smaller size valves.
- 10hp - 1.600" intake and 1.375" exhaust, with a 1" venturi Carter or Kohler carburetor.
- 12hp - 1.700" intake and 1.450" exhaust, with a bored-out 1.2" venturi Carter or Kohler carburetor.
- 14hp - 1.800" intake and 1.500" exhaust, with a bored-out 1.2" venturi Carter or Kohler carburetor.
- 12hp/30 c.i. (NQS) - 1.800" intake and 1.500" exhaust, with a large Mikuni or other make of large throttle bore carburetor.
- 16hp (37 c.i. Missouri Super Stock) - 1.900" intake and 1.600" exhaust, with a bored-out 1.2" venturi Carter or Kohler carburetor.
- 16hp/50.5 c.i. (NQS Super Stock/Missouri Modified) - 2.000" intake and 1.700" exhaust, with a large Mikuni or other make of large throttle bore carburetor.
The sizes above flows best according to the cubic inch displacement and when using a 1.200" carburetor venturi. By the way - the 10hp and 12hp intake valve can be used in the exhaust hole, with the seat removed. And remember this when installing larger valves: The larger the valve head diameter (and higher the lift the cam has), the larger the valve cavity (part of combustion chamber) will need to be (for clearance around and above the valve). A larger combustion chamber will have less compression which means less horsepower. But, more power and compression will be regained if the valve job, use of the right cam and proper valve timing are all matched correctly.
And when installing offset valve guides, take into consideration that if the block has valve seat inserts, with the insert(s) removed, if the face of the oversize valve will make contact with the part of the seat that's farthest from the piston.
Remember, when enlarging the ports, especially the intake port, make it the same size as the venturi in the carburetor or an air restriction (bottle neck) will occur, and the engine will not breath sufficiently at higher rpms. The exhaust port needs to be about 22% smaller than the intake port.
Using a Small Block Chevy Intake Valve in a Kohler Engine -
Small block Chevrolet V8 and certain Chevy V6 engine stock
intake valves will work in a 10-16hp Kohler engine with excellent results,
even with offset valve guides. The 1.72", 1.84", 1.92" or 2.02" diameter
intake valve can be used for the intake in a 10-16hp [pulling] engines. The
1.94" and 2.02" Chevy valves will work for the intake in a 16hp/50.5 c.i.
[pulling] engine.
Stock intake valves works great as an exhaust valve in a pulling engine because the engine doesn't run long enough for the valve to burn or warp.
The valve stem will need to be shortened next to the keeper groove (make the overall length the same as Kohler valves, which is 4.635".), and the oil seal groove becomes the keeper groove. Being the Chevy valve stem is 11/32" in diameter, the valve guide(s) will need to be enlarged with an 11/32" reamer so the valve stems will have proper clearance.
The Chevy valve head will also need to be lightened and the face (and seat) should be ground at a 30º angle for the intake (for maximum air flow), and 45º for the exhaust. And either the Chevy retainers can be used or stock Kohler retainers can be used with the Chevy valve. But the Chevy keepers or locks must be used because of the larger diameter valve stem. The Chevy retainer will need to be turned down in a metal lathe to fit the smaller aftermarket valve springs that's made for Kohler pulling engines. Don't try use Chevy valve springs in a Kohler engine! They're way too stiff and much too difficult to install in a Kohler engine. Actually, they're almost impossible to compress for installation in a Kohler engine.
Remember to do this when installing bigger valves -
When
installing larger valves, the tapered area on the engine block around each
valve must be ground away for full airflow into and out of the combustion
chamber. The area just outside of the valve seats next to the piston area
(the area where the valves are angled down into the block) needs to be ground
away also so the engine can have full air flow in and out of the cylinder.
This is very important because if it isn't opened up there, it'll starve
the engine for air/fuel. To check this area for adequate clearance, with
the head removed, rotate the engine so each valve is fully opened and then
insert a wooden dowell or soft aluminum rod (to keep from scratching the
valve face and seat) that has the same diameter of the lift of the cam to
use as a plug gauge. Grind the tapered area around the valves enough so with
the valves installed, you can fit a soft metal (aluminum rod) between the
valve face and seat with the valves at full lift. This is how you get full
airflow into and out of the combustion chamber. With the metal ground away,
the rod should fit snug under the valve head and seat all the way around
each valve. If the plug gauge doesn't fit, the metal on the block just outside
each valve seat needs to be ground away, especially toward the piston. Be
extremely careful not to let the grounding stone touch the finished seats
though!
If you're concerned about doing the above will decrease the compression ratio, well, it will somewhat. But, by doing so, it'll allow the engine to draw in much more air, producing more compression. In return, it'll produce more power and rpm. I know, we've done this many times with excellent results.
And the only way I found to grind this area of the block is to use a die grinder with a 1" diameter rounded end stone. To keep the stone from touching the valve seat, I rest the side of my right hand on the top of the block (I'm right handed) and slowly and very carefully grind away the metal.
Information About Valve Guides - Top of page
How to Remove and Install Pressed-In Cast Iron Valve Guides in a Cast Iron Block Kohler Engine:
-
Acquire a 1/2" diameter x 5"
long grade 8 bolt. Machine the threads down to .300" so it will become a
pilot to fit inside the valve guide. This will be the driver tool.
- Remove the valves, springs and retainers. Measure old guides to insure if they are worn or within specs.
-
To remove worn guides:
- On the K141 (6¼hp), K160 (6.6hp), K161 (7hp) and K181/M8 (8hp) flathead single cylinder and all flathead twin cylinder Kohler engines, if the lifters (and camshaft) are installed, break off half of the guide inside the valve spring compartment with a flat chisel and a medium size hammer, and then use the machined bolt as mentioned above and a big hammer to drive the remaining guide out and into the valve spring compartment. If the lifters and cam isn't installed, just drive the entire guide out into the valve spring compartment without breaking it off first.
- On the 10-16hp flathead single cylinder Kohler engines, rather if the lifters (and camshaft) are installed or not, drive the entire guide out into the valve spring compartment with the machined bolt and a big hammer.
- Install the new guide with the machined bolt with a flat washer under the pilot so the guide will be flush inside the intake and exhaust pockets.
- The new guides may need to be reamed out with a 5/16" reamer so the valve stems will have proper clearance.
FYI - In most cases, worn valve guides don't necessarily need to be replaced. They can be repaired with a thin-wall bronze liner, like the ones installed in automotive cylinder heads. Also, a bronze liner will last longer than a cast iron guide because bronze retains more oil for better lubrication for the valve stem.
Installing Offset Valve Guides -
The
best way to gain more power and torque from any engine is to increase its
compression ratio. On a flathead (valves in block) engine, the way to do
this is by moving the valves closer to each other and closer to the piston
with the use of offset valve guides. As a result, the combustion chamber
can be made smaller and the relocated valves will flow better. Machining
for oversized valves (minimum 1.550" for the intake and exhaust) must be
installed in order to do this. Stock valves cannot be used with offset guides
because the offset guides will move a portion of the valve head off the seat.
And an minimum oversized valve head diameter of 1.550" must be used with
a guide that's offset at .085". (Stock valves = 1.375". Guide moved .170"
[.085" x 2]. .170" + 1.375" = 1.545". Use a valve of 1.550" size.)
Installation of new valve guides usually doesn't require new valves. Although the valves will need to be reground so they will seat better. And to remove the guides, first remove the valves. Then use a long 5/16" grade 8 bolt with a nut threaded on it and a heavy hammer to drive the guides out and into the valve spring compartment. Install new guides by driving them in with a hammer until they are flush with the port. The offset guides may need to be enlarged with a 5/16" reamer so the valve stems will have proper clearance. There are 3 ways to install new valve guides:
- If an engine is going to run stock diameter valves, and if the old guides are worn, or if you want to upgrade them for high-performance use, leave the OEM valve guides in the block, and have them center-reamed to accept a thin-wall bronze liner.
- For installation of oversized valves, install new guides that's made of 5/8" diameter solid bronze with an offset center hole.
- Or, for installation of oversized valves, install 5/8" diameter mild steel as a shell with an offset center hole, to accept a thin-wall bronze liner.
Bronze is hard material and it retains oil because it's porous. Go here to learn more about bronze valve guides: K-line Interrupted Spiral Guide-Liners. To help the guides and valve stems last longer, drill a small (1/8") hole crossways through the lower part of each guide in the valve spring compartment so the crankcase oil will help keep the valve stems and guide well lubricated and cool. This will reduce stem-to-guide friction (wear) and it'll help promote smooth valve action, which will help increase horsepower slightly and longevity of the guide.
To remove the valve guides from the 10-16hp Kohler engines, drive them out into the valve spring compartment with a 5/16" diameter grade 8 bolt with a nut threaded on the bolt and a big hammer. Also, after many years of use, some guides can be very stubborn to remove, especially the exhaust one. So instead of removing the old guides from an engine with stock valves, have them reamed to accept a thin-wall bronze liner. Besides, all new OEM guides needs to be reamed for the valve stem to fit anyway. So why not have a bronze liner installed instead? Installing CLASSIC Bronze-Liners
When thin-wall bronze valve guide liners are installed, first, the valve guide is reamed the same o.d. as the liner. Then the liner is inserted in the guide, and an air-operated valve guide driver is used to expand the liner in the guide so it'll have the correct clearance for the valve stem.
To bore the offset center hole in a guide, drill the hole in the guide approximately .085" offcenter with the guide firmly clamped in a super spacer (with a self-centering 3-jaw chuck) that's fastened on the table of a vertical milling machine. When drilling bronze, use a non-oily lubricant, such as brake cleaner.
Advertisement:
| If you need any of the tools listed below, please contact A-1 Miller's
Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203-9136
USA | Phone: 1-573-875-4033.
Please call Monday-Friday, 9am to 5pm, Central time. If no answer, please
try again later. (When speaking with Brian, please be patient because
I stutter.) Fax: 1-573-449-7347.
E-mail:
pullingtractor@aol.com. You can
also contact us through Yahoo! Messenger:
|
| Valve Guide Removal and Installation Tool. Use with a big hammer
to remove and install valve guides. $10.00 each, plus shipping &
handling. |
Straight Flute High Speed Steel Precision Chucking Reamers.
Perfect size to ream out new valve guides to OEM Kohler specs or installing
Chevy valves in Kohler engines. Will not make valves too loose or too tight.
|
How to locate where to machine the cylinder head for the valves...
- Strip the engine down to the bare block.
- Fasten the billet cylinder head and head gasket on the block with a couple of bolts.
- Run a 5/16" diameter steel rod that has a sharp point on one end into each valve guide from inside the block with the pointed end toward the head.
- Using a hammer, lightly tap on the end of the rod so a small impression (punch mark) will be created on the head. These punch marks are the locations for the center of the valve heads.
-
Using
a machinists' inside divider caliper, scribe a circle (radius) around each
punch mark the same diameter as the valve heads, plus approximately .100"
for additional clearance around the valves.
- Now the cylinder head can be machined for the valve cavities and combustion chamber.
How to check for proper valve clearance between the valves and cylinder head...
- For the 10-16hp engines, set the valves at their respective clearances. (See above.) Adjustment is made with a flat feeler gauge and with the lifter held in place with a slender 1/2" open-end wrench and turning the adjuster screw in the lifter with a 7/16" open-end wrench. Make sure the lifters are on the base circle of the cam lobes, too.
- Place a small amount of modeling clay on each valve head and under the head in each valve cavity. (Place some oil on each valve and valve cavity to keep the clay from sticking to either.)
- Place the head and gasket on the engine and tighten down a couple of head bolts.
-
Rotate the crankshaft slowly by hand 360°. If it stops rotating,
do not force it, because damage may occur to the camshaft. Remove
the head and see if one of the valves made contact with the
head.
-
If the crankshaft rotates freely
after 360°, remove the head and use the depth gauge on a dial or digital
caliper to determine the thickness of the clay. The clay should have a minimum
thickness of about .070".
- Remove metal from inside head (valve cavities) as necessary to gain proper clearance.
- Clearance around the valves should be the same as above the valves (valve shrouding).
- Repeat steps 2 through 6 to gain proper valve to head clearance.
FYI - One valve I found is an exhaust valve made for a Wisconsin engine. It's a Perfect Circle part #211-1832. It has a 1.590" diameter head and 5/16" diameter stem. Overall length is 4.865". But Kohler valves are 4.635" in overall length. This means the stem will need to be shortened .230" and a new keeper groove will need to be machined. Check at a local auto parts supply store for this valve. They can usually get any size or type of valve you want.
If one is extremely careful, bigger valves can be
installed using a pneumatic (air-operated) die grinder with an ordinary grinding
stone and an electric valve seat grinder. There's no need to install valve
seat inserts either. Just cut or grind the new seats directly into the cast
iron block. For best flow and compression, the high point of the seat needs
to be even with the deck of the block. If the seat is made too deep, valuable
flow and compression will be lost! Most blocks can be decked to regain the
compression, though. (If rules allow it.)
For best valve flow, cut or grind the intake valve face and seat at a 30° angle, and the exhaust valve face and seat at a 45° angle. Give the intake seat about a .030" width, and the exhaust seat about a .060" width. Make the valve face mating surface near the edge of the valve, too.
For quality stiffer-than-stock valve springs, oversize valves, lightweight retainers and hardened keepers, contact Lakota Racing (http://www.lakotaracing.com), Midwest Super Cub (http://www.midwestsupercub.net) or Vogel Manufacturing Company (http://www.vogelmanufacturing.com). They offer light-weight valve springs that's stiffer than stock springs, but won't normally break a Kohler cast iron camshaft with a lift up to .432".
For durable stainless steel or light-weight titanium stock-size and oversized valves, along with stiffer springs, heavy duty retainers and keepers, contact either Lakota Racing, Midwest Super Cub or Vogel Manufacturing Company.
What is Port and Polish (or Porting and Polishing)? - Top of page
"Porting" is when the intake and exhaust ports (runners) in a flathead engine block or OHV cylinder head are made larger in volume so more air/fuel can enter the combustion chamber and the exhaust gases can exit quicker so the engine will produce higher compression pressures which results in more power and torque at higher rpm.
"Polishing" is when the intake and exhaust ports are made smooth so the atomization mixture of the air/fuel isn't interrupted. Polishing of the exhaust port also helps the exhaust gases to exit quicker from the engine. Actually, by leaving the intake port "rough" and not smooth, this will cause the fuel to atomize into smaller particles, and mix better with the air, allowing the engine to produce more power. But it's best to have exhaust port smooth so the escaping gases will exit the combustion chamber with less obstruction.
An Easy and Sure Way to Determine the Port Size and Flowing the Ports -
When enlarging the ports and to determine the correct size of each port, make a couple of "plug gauges" from a 1.200" diameter fender washer for the intake port (to match a 1.200" carburetor) and a 1.000" washer for the exhaust port, which can be mounted on a long bolt. Click HERE for a better understanding about the shape of the intake runner port. When grinding the ports, feel each port for smoothness. Give the intake runner a fine hone finish. This will help to atomize the fuel with the air. Do the same with the exhaust runner. Because any roughness will disrupt the atomization of the fuel with the air, causing loss of power.
For best engine performance, the port runners should be enlarged
to match the diameter of the carburetor's bore. To port out an engine block,
a pneumatic die grinder with a large, long pointed stone could be used, but
this method is VERY time consuming and tiresome. It takes about 5-6 hours
of labor with a die grinder... and a good air compressor. For much faster
and accurate results, a 1/2" pneumatic [air operated] drill with a large
quality [high speed steel] drill bit can be used. This is how I enlarge the
ports on an engine. After I "drill them out," I then use a pneumatic die
grinder with a 1" diameter pointed stone for a smooth finish. It takes only
about 10 minutes to enlarge the ports in an engine with a large drill bit
and a pneumatic drill. Use a large diameter drill bit (either 1.07" or 1.2")
to match the diameter of the carburetor's throttle bore. The intake port
doesn't have to be no bigger than the carburetor's throttle bore that's going
to be used on the engine. When facing the intake port, hold the drill bit
so it's positioned slightly downward and angled slightly to the right for
best air flow through the port and into the combustion chamber. The drilling
process should leave the port pretty smooth and straight. But if there are
a few rough spots, they can be smoothed with a die grinder/stone. Don't use
an electric drill, even a heavy duty one, to port out an engine! A very large
drill bit will likely to "catch" or get "hung up" in the cast iron port during
the drilling process and this will cause the reduction gears in the drill
to strip out.
If an engine has hardened exhaust valve seat(s), unleaded gasoline has no effect on the wear of the seat(s). In fact, all engines built nowadays or since unleaded gas was first introduced have hardened exhaust valve seats. Valves are unaffected by unleaded gas. Also, unleaded gas helps to keep the combustion chamber free of carbon deposit buildup.
Information about Lifters
-
Used lifters can be successfully reused with a new or used camshaft. What needs to be done to prevent wear to the cam lobes is scuff the face of the lifters with 600 grit sandpaper until all the shiny surface is gone. This will provide a new wear pattern for the lifters and cam lobes. But if the old lifters are worn or rusted, then it's best to replace them with either good lifters or new ones. And if the cam lobe(s) are worn, then definitely replace it with another good camshaft.
Information
about the Camshaft and How to Degree in a Steel Cam
Top of page
Installation of a special camshaft is important if increased performance is to be obtained. Simply put, the cam tells the valves what to do, when to do it and for how long. Performance cams lift the valves higher and hold them open longer in relation to piston travel than stock camshafts. (This is otherwise known as "valve lift" and "duration.") Air is very flexible. It can be compressed as well as it can be expanded. So when an engine revs at high rpm, air doesn't have time to exit back through the valves, so it becomes trapped within the combustion chamber. In that way, more air/fuel mixture is drawn into the cylinder. This is what builds up the compression with a long duration cam so the engine will produce more power at higher rpm. In addition, a larger portion of the burned gases will be expelled from the engine. Also, cylinder head clearance, improved carburetion, larger valves and stiffer valve springs are a must in order to take full advantage of a bigger cam. And always use wide base lifters with a cam that has a lot of lift and duration. Use of the right cam and proper valve timing can help an engine come to life and scream down the track!
The proper installation of the camshaft is very important for full power and torque. The camshaft is the heart of your engine and if it isn’t installed properly, the whole engine will run sluggish. Camshaft degreeing is the one most important thing that can be done to an engine. If the camshaft isn't degreed in, odds are it will usually be too far advanced or retarded. I highly recommend that you properly degree your camshaft. Step-by-step method of how to degree your camshaft is listed below. If your camshaft can move back and forth in your engine, you are losing power. When your camshaft moves forward, your ignition timing becomes retarded, which makes your engine run sluggish.
If you want to get a lot of power from your engine, and all you want to do is install a big cam with a lot of lift and duration, well, installing a big cam alone in an engine won't help it to produce a lot of power. The reason is because engines are basically an air pump. Big cams moves A LOT of air in and out of an engine. They also perform best at very high rpm. Here's some things an engine will also need with a big cam:
-
It'll
need bigger valves, stiffer-than-stock valve springs and wide base lifters.
- It'll need extensive porting and polishing.
- It'll need a much bigger carburetor than Kohler makes.
- It'll need a billet aluminum cylinder head for valve clearance.
- And it'll need a steel flywheel for safety.
BE AWARE! Lifts
up to .432" can safely be put on the Kohler cast cam. A Kohler cast iron
camshaft with more lift than .432" lift that has both lobes welded-up and
reground for more lift and duration is not expected to live long with
stiffer-than-stock valve springs. The more lift a cast cam has, the more
likely it is to break. It's only a matter of time. They break next to the
gear. The reason they break is because the support pin flexes under load
(valve lift), and cast iron doesn't. That's why if a cast cam is used, it's
best to use a support pin made of hardened steel.
When rebuilding a Kohler engine or installing
another [cast] camshaft, check the cam pin for wear. If it's worn, this will
allow the cam to "wobble around" at high engine rpm resulting in erratic
valve action, and it'll cause the ignition timing to be very erratic, which
will cause the engine to run erratic and lose power. A cam running on a worn
pin will even make the engine "pop" and backfire out the exhaust at high
rpm.
The OEM cast iron camshaft in the 4-16hp Kohler engines is held in place by a single long pin that goes in from the flywheel end of the block, through the cam and is wedged in the PTO side of the block. To remove it, use a long, hardened 3/8" diameter (for the 7hp & 8hp engines), 7/16" diameter (for the 10-16hp engines) bolt or steel rod and a medium size hammer, and drive it out from the PTO side of the block. It comes out on the flywheel side. Replacement is in the reverse order of removal. Be sure to reset the valve clearances after the new pin is installed. As the cam pin is driven out, be sure that the shim(s) (very flat washers) that's on the end of the cam towards the flywheel end don't fall out of place.
When using a cast cam in an engine that runs at wide open throttle, be sure to install heavier-than-stock valve springs to prevent valve float at high rpm. And make sure to use high zinc oil, not a multi-weight for newer engines. Without the zinc, it will wear the lobes. High zinc examples are: Delvac, Cen-Pe-Co, Amzoil Dominator, Red Line, Brad Penn, Rotella, Joe Gibbs, and others. Just check it out before you buy.
How a Long Duration Camshaft Works -
An engine that has a stock camshaft and when it is at an idle speed, about 95% of the air that enters the engine becomes trapped within the combustion chamber. This does not change as engine speed increases. But with a long duration cam that has "humped-up" lobes, at idle speed, some of the air that enters the combustion chamber, and being the valves stay open longer, exits through the intake and exhaust valves. (This is why engines with a high-performance camshaft idles rough. The more duration a cam has, the rougher the engine will idle.) Anyway, as engine speed increases, and being air can be compressed as well as it can be expanded, the air will eventually become trapped within the combustion chamber. This "trapping of the air" builds up the pressure within the combustion chamber. Thus, allowing the engine to produce more power at higher rpm. The faster an engine revs up, the more air will become trapped in the combustion chamber. (This is also why engines with a high-performance camshaft runs smooth as engine speed increases.)
Have you ever noticed that when the piston is on the exhaust stroke, how each valve is slightly open? Well, that's called valve overlap. It's normal on all camshafts. It scavenges the exhaust gases from the combustion chamber and creates more vacuum for the incoming air/fuel. It happens only when the piston is on the exhaust stroke. And both valves are fully closed on the compression stroke.
The Cause of Carburetor Flooding at Slow Idle with a Long Duration/High Performance Camshaft - Top of page
Sometimes when using a long duration/high performance camshaft, despite if the engine has a modified or stock carburetor, if the engine idles for a long period of time, it may run rich on fuel at slow idle speeds. What happens is with a long duration cam, intake vacuum is low and with a single cylinder engine, excess fuel builds up in the intake extension/port. Any engine that has a long duration camshaft have low vacuum at slow idle speeds. The longer the duration, the lower the vacuum. What causes excess fuel to build up in the intake is the long duration of the cam lobes holds the [intake] valve open longer, and at slow idle, the pressure of the piston blows some of the air/fuel back into the intake tube. The more duration a cam has, the worse this will be. As the engine is accelerated, black smoke or raw unburned fuel will blow out the exhaust until the fuel is cleared out of the intake tube. With the engine running well above idle, air becomes trapped within the combustion chamber and the piston don't have time to blow any air/fuel back into the intake. This happens with gas, E-85 or 100% methanol fuels, and there's nothing that can be done about it. There's probably nothing wrong with the carburetor, and nothing can be done to the idle circuit to prevent this. Just make a simple adjustment with the idle air/fuel mixture screw so the engine idles smoothly, and don't allow the engine to idle for a long period of time.
Kohler's Old Style Two-Piece Camshaft -
If
you've ever seen a Kohler camshaft that's made in two pieces (not broken
in two), these were original equipment from the factory and came in all K141
6¼hp engines and the very early K241 10hp engines up till 1964. These
cams were made before the automatic compression release mechanism came into
existence. Instead, theses cams have an ignition timing retard mechanism.
With this type of cam, the engine would start under full compression, making
it hard on the starter/generator (if it wouldn't start right away, the battery
would eventually drain). At cranking speed, the ignition timing is positioned
at 0° TDC so the engine wouldn't "kick back" under full compression.
After the engine starts, spring-loaded flyweights on the cam gear automatically
rotates the point lobe slightly, advancing the timing to 20° BTDC so
the engine can produce full power. These cams have the same lift and duration
as the newer, one-piece camshaft with the automatic compression release
mechanism.
If you choose to reuse this camshaft to keep
the engine "all original," when reinstalling the cam in the engine block,
make sure the timing marks on both the cam gear and ignition cam (points
lobe) are aligned, or the ignition timing will be 180° off and the engine
will not start! Also, make sure the springs that's on the flyweights are
properly positioned on the points lobe so there's pressure on each spring
and so the timing advance flyweights can move inward and outward when the
engine is shut down, and started up.
NEVER INSTALL A CAMSHAFT
DRY! Always lubricate the pin and inside the camshaft with motor oil
or grease before reinstalling the cam in the block! Failure to do so, just
after starting the engine, friction from dry running will cause the cam to
seize on the pin. Severe damage to the pin, cam and engine block will
result!
When setting the ignition timing on the engine
with this type of cam, set the points so they just begin to open with the
piston positioned on the compression stroke at 0° TDC (T mark on the
flywheel). When the engine starts, the points lobe automatically rotates
slightly, advancing the timing to 20° BTDC. Don't set the timing at
20° BTDC (S mark on the flywheel) with this type of cam! Because setting
it at 20° BTDC will cause the engine to "kick back" (when the
flywheel/crankshaft suddenly and violently rotates in the opposite direction
of normal rotation) when trying to start. And if it does start, the timing
will automatically be advanced to 40° BTDC, which will cause the engine
to run too hot and prematurely wear out. Return
To Previous Web Page.
Removing the Camshaft -
Kohler's cast iron camshaft
is held in place by a 1/2" diameter steel pin that goes all the way through
the cam and engine block. The camshaft is removed by first removing the flywheel,
aluminum bearing plate, piston/rod assembly and crankshaft. Then use a long
steel rod that's slightly smaller than 1/2" in diameter and a medium size
hammer to drive out the pin from the PTO end of the block.
(See the picture to the right.) And when reinstalling the
pin, drive it in from the flywheel side until it's flush with
the block. The hole in the PTO end of the block is tapered to secure the
pin in place.
NEVER INSTALL A CAMSHAFT
DRY! Always lubricate the pin and inside the camshaft with motor oil
or grease before reinstalling the cam in the block! Failure to do so, just
after starting the engine, friction from dry running will cause the cam to
seize on the pin. Severe damage to the pin, cam and engine block will
result!
To prevent damaging
or cracking the engine block, drive out the camshaft pin from the PTO end
towards the flywheel end. Do not drive out the pin from the flywheel
end! Doing this could also crack or break the camshaft! The hole on the
PTO end of the block for the cam pin is tapered. This is what secures the
pin in place.
When reinstalling the cam
pin in the block, through the camshaft and into the hole in the PTO end of
the block, this hole is tapered and it actually "squeezes" the pin as it
is driven into the block so it won't rotate with the cam, and it's supposed
to seal the oil from leaking after the pin is installed. But on occasion,
the hole will leak oil. Kohler didn't originally apply sealant in this hole
for some reason. To prevent an oil leak, clean the oil from inside the hole
and the block with cleaning solvent (paint thinner), allow to thoroughly
dry, and then fill the hole with
Clear RTV Silicone Adhesive
Sealant.
The camshaft, lifters and cam pin in the 10hp, 12hp, 14hp, 16hp engines will all interchange. Their camshafts all have the same lift, too. The only exception is the cam that's designed for the 18hp OHV single cylinder cast iron block Kohler engine. It has the same lift as the flathead engine cams (.324"), but increased duration from 223º (flathead cam) to 256º (18hp cam). The 18hp cam will help the 10-16hp K-series and Magnum flathead engines produce more power and torque up to approximately 4,000 rpm. Because of it's limited duration, it won't help to increase the compression much above 4,000 rpm, which makes it ideal for use in a stock governed engine. By the way - the 18hp cam doesn't have enough duration to make the engine have a "loping" sound at idle. It makes the engine sound like a stock short-duration cam.
Advertisement:
| If you need any of the items listed below, please contact
A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia,
MO 65203-9136 USA | Phone:
1-573-875-4033. Please call Monday-Friday, 9am to 5pm, Central time. If no
answer, please try again later. (When speaking with Brian, please be patient
because I stutter.) Fax:
1-573-449-7347. E-mail:
pullingtractor@aol.com. You can
also contact us through Yahoo! Messenger:
|
|||
 Nylon Governor
Gears. Good for up to 4,000 rpm. OEM Kohler part # A-235743-S.
|
 Cast Iron Governor
Gear. Good for above 4,000 rpm up to wide open throttle. Will not explode
or flex at high rpms like the nylon governor gears sometimes do. OEM Kohler
part # A-237031. (Discontinued from Kohler.)
|
||
 New hardened steel
thrust washer for nylon or cast iron governor gear. Kohler # 237022-S.
|
 3/8" diameter
stub shaft for governor gear in 6¼hp-16hp Kohler single & twin cylinder
flathead engines. Kohler part # 235125-S.
|
||
 Genuine OEM Kohler
one-piece cast iron camshafts for Kohler K-series and Magnum models K141
(6¼hp), K160 (6.6hp), K161 (7hp) and K181/M8 (8hp) flathead cast iron
block engines. NOTE: The 6¼hp & 7hp cams can't be used in
the 8hp engine due to the 8hp's longer stroke.
|
|||
Genuine OEM
Kohler one-piece cast iron camshafts for Kohler K-series 10hp-16hp K241-K341
and Magnum M10-M16 flathead cast iron block engines.
|
|||
 Reground Low
RPM Performance Torque Cam
Reground 4,000 rpm performance torque cast cam for 10-16hp flathead Kohler engines. This cam profile has increased duration, legal stock lift and will pass tech for an OEM Kohler stock cam, but it adds about 3 more horsepower and 2 ft. lbs. of torque to an average stock engine with more lugging power than the 18hp cam. And it'll add more power and torque with a performance valve job, enlarged ports and a bored-out carburetor. This cam sounds just like an OEM stock cam. You can't hear the difference out the exhaust. It's perfect for a competing stock pulling tractor or for heavy yard work. To prevent breakage, use only OEM or light-weight Stock-Altered single valve springs with this cam. This cam installs just like the OEM cam. Just thoroughly lubricate the inside with motor oil, align the timing marks on the gear teeth, set the end-play and valve clearances to OEM specs, and it should be good to go. NOTE: When the cam lobes are reground, metal is removed from the base circle which reduces the diameter of the base circle in order retain maximum lift at the point on the lobe. The ramps on the lobes are also "rounded" to give the cam more duration. The cam grinder's stones are about 1" wide, so when I get the cams back from being reground, I have to grind metal away from the sides of the base circles so the edge of the lifters won't "ride up" on the unground areas and hold the valves slightly open when they're supposed to be fully closed. I have to do this to every reground cam I have in stock. If everything else is set up correctly in your engine, this cam should work just fine. So there's no need to be concerned about the metal being ground away when you receive the cam. Also, some of the cams I have, the points lobe is slightly worn (it's hard to find a 100% good cam nowadays) and I include a stainless steel points pushrod with a flared end to make contact with the unworn areas of the lobe. The pushrod will need to be installed from inside the block before the cam is installed.
These cams are $150.00 each outright, plus shipping & handling.
$25.00 core charge, when you send me your stock OEM camshaft. Core must be
in good condition, never reground before with gear teeth in good condition
and minimal wear on points lobe. When sending a core to us, be sure to include
a note with your name, mailing address, phone number and that you want to
trade the cam in as a core. We will then deduct $25.00 from the price of
the torque cam. Please send your cam core to: A-1 Miller's Performance
Enterprises, 1501 W. Old Plank Rd., Columbia, MO 65203-9136 USA.
|
|||
| Your Kohler K-series 10hp-16hp K241-K341 or Magnum M10-M16 flathead cast iron block engine camshaft reground to the 4,000 rpm torque specs: $115.00 labor, plus return shipping & handling. | |||
 Valve Lifters
(Tappets) for Kohler K-series and Magnum single cylinder engine models K241/M10
(10hp), K301/M12 (12hp), K231/M14 (14hp) and K341/M16 (16hp). OEM Kohler
part # D-235327-S.
|
|||
 New Camshaft
Pins for Kohler Cast Iron Block Engines.
|
|||
 Camshaft End Thrust
Washers/Shims/Spacers.
|
|||
And if you're wondering, all of Kohler's stock camshafts are removed by driving out the steel pin that it rides on from the PTO end of the block (opposite flywheel end) with a hammer and long steel pin that's slightly smaller than 1/2" in diameter. Also, there should be one or two shims on the pin. Be sure not to loose them. You'll need them when you reinstall the cam.
NOTE: The 18hp cam works great for more power in a 10hp and 12hp engines, but it won't do quite as much as the cubic inches increases. Although it will work great in the 14hp and 16hp engines, but it creates less noticeable power increase in the 14hp and especially the 16hp engine. However, it does help in the power increase in a 16hp, it's just less noticeable because of the bigger cubic inch displacement. A "mild-performance" cam, such as the 18hp cam, works better in engines with smaller cubic inches. A somewhat bigger cam is required as the cubic inches are increased. Because bigger engines needs to draw in and expel more air (at 4,000 rpm with stock valves), and the 18hp cam has it's limits when used in the bigger engines. And because of it's short lift and duration, it makes it's most power up to around 4,000 rpm.
NOTE: Use stock OEM valve springs with a stock OEM or 18hp cam if an engine is going to turn 4,000 rpm or below. And use Stock-Altered (single) valve springs for above 4,000 rpm. Because cast iron is brittle, do not use double (Super-Stock) valve springs with the 18hp or any [welded up] OEM camshaft! Also, with double springs, the compression release lever on the cam could break off. And be gentle when handling a cast iron camshaft! If the cam is mishandled, the lightweight spring that controls the compression release mechanism could come off the levers when installed in the engine. If this happens, the engine would crank over under full compression, making it very hard or impossible to start.
When having a camshaft
reground, trust only places that use a specialized precision cam grinding
machine. Because if the lobes are "hand ground" or if ground any other method,
the cam may not work as well.
The OEM 18hp cast iron camshaft that originally came in the Kohler model K361 18hp OHV engine is discontinued from Kohler. If you're lucky, you might find one from old stock. The part number for it is 45 010 05S. Or you can send your 10-16hp OEM flathead Kohler engine cam to us, and have it reground for increased duration up to 4,000 with stock lift for $125.00, plus return shipping & handling. This cam profile adds about 2-1/2 more horsepower to an average engine. When sending a cam to us, be sure to include a note that you want the cam reground for increased duration up to 4,000 with stock lift. List your name, mailing address and phone number, too.
If you have a cam that was broke in two by a thrown connecting rod, save the hair-like or light-weight spring from the compression release mechanism. It can be used on another cam that may not have one.
| Camshaft | OEM Kohler Flathead Engines (10hp, 12hp, 14hp & 16hp) Cams (Average) |
OEM Kohler 18hp OHV Cam |
Reground "Cheater" Cam |
| Exhaust Opens, Degrees BBDC |
50° | 50° | 60° |
| Exhaust Closes, Degrees ATDC |
20° | 25° | 36° |
| Inlet Opens, Degrees BTDC |
30° | 52° | 40° |
| Inlet Closes, Degrees ABDC |
70° | 79° | 80° |
| Overlap, Degrees |
50° | 77° | 76° |
| Exhaust Duration, Degrees |
250° | 255° | 276° |
| Inlet Duration, Degrees |
280° | 311° | 300° |
| Maximum Lift Exhaust, in. |
.301" | .306" | .311" |
| Maximum Lift Intake, in. |
.308" | .325" | .317" |
| Recommended Lash Settings | |||
| Exhaust, in. | .017" | .017" | .014" |
| Inlet, in. | .008" | .008" | .009" |
Setting the Valve Timing For Cast Iron Kohler Cams Without a Machined Adjustable Gear -
If you're planning to use a
factory stock cast iron cam (such as a reground Kohler cam or the 18hp OHV
Kohler cam), or if the cam grinder person ground your high performance cast
cam "right on the specifications," it shouldn't need to be degreed in. Just
install it in the engine, usually along with a thin and thick shim (.005"
& .010", respectively) toward the flywheel end, and it should be set
pretty close to specs, if not right on it. But steel cams with an adjustable
gear will probably need to be degreed in according to the provided specs
sheet. Install shim(s) with a steel cam only to prevent wear on both the
camshaft and engine block. To accurately set the valve timing on a Kohler
or virtually any 4-cycle engine, simply align the punch [timing] mark on
the camshaft gear, which is located between two gear teeth, with the groove
or [timing] mark on or next to the crankshaft gear, which is located at one
gear tooth. If there's no timing marks or if there's multiple marks on either
gear (these can be confusing), to set the correct cam to crank timing on
a single cylinder engine, with the crankshaft installed in the block, position
the piston at true Top Dead Center (TDC). True TDC is when the piston is
at the very top of the cylinder. Now install the camshaft and valves, and
then check for correct alignment by rotating the crankshaft 180° so
the piston is at true TDC on the exhaust stroke. Slightly rock the crankshaft
back and forth by hand. When one valve opens slightly and the other closes
slightly, and vice-versa, and when the piston is either slightly after or
before TDC while rocking the crankshaft, the valve timing is set correctly.
On a multiple cylinder engine, align the cam and crank gears with the piston in the #1 cylinder positioned at TDC on the compression stroke. On a twin cylinder engine, the #1 cylinder is the one closest to the flywheel. On an automotive engine, the #1 cylinder is the one closest to the front of the engine, or harmonic balancer. Align the cam gear tooth with the crank gear, and to check for correct cam to crankshaft alignment, rotate the crankshaft 180° so the #1 piston is at true TDC on the exhaust stroke. Then slightly rock the crankshaft back and forth by hand. One valve on the #1 cylinder should slightly open and the other valve on the same cylinder should slightly close. The piston should be either slightly after or before TDC while rocking the crankshaft, this is when the valve timing is set correctly.
Installing a Steel Camshaft that Has an Offset in the Center - (for long stroke engines)
When
installing a steel camshaft that requires two separate support pins, you'll
need to cut a Kohler pin in half. But first measure the depth of the pin
holes in the cam and the engine block to determine each pin length. Then
drill the pin hole that's in the PTO end of the engine block to 1/2" diameter.
To retain the pins in the block and to keep them from turning with the cam,
a diagonally drilled hole must be made and some 1/4-20 threads must be cut,
then tighten an Allen head set screw into each threaded hole to retain the
pins. Be sure to apply
Clear RTV Silicone Adhesive Sealant on the PTO end pin
to keep oil from leaking out, too. Also, don't forget to drill and tap some
1/4-20 threads into the end of each pin so a 1/4" bolt can be threaded into
them so they can be removed from the block later.
To install needle bearings in
a block for a camshaft that will accept them, the holes for the cam pin will
need to be precision bored (enlarged) to .6875" (11/16") in a milling machine
exactly dead center. The exact dead center of the holes are found by using
a centering indicator. If the holes are bored off-center just a few thousands
of an inch, the cam and crank gear teeth won't mesh correctly and the lifters
will wear the cam lobes prematurely. By the way - the needle bearings that's
in Kohler's balance gears will work perfect for a cam that requires them.
Always
degree in a high performance steel cam to get maximum power from it. Why
is this so important? Timing of the valves in relationship to piston travel
plays a huge role in how well an engine performs. The key to accurate cam
timing is to find exact Top Dead Center (TDC). The best method to
find TDC is to use a degree wheel, dial indicator with a magnetic base and
a piston stop. Or for a piston stop, on a flathead engine, a long reach spark
plug can be used, and the cylinder head can be positioned it so the spark
plug is over the piston.
A maximum of 3.500" stroker crank can be used with the pin-through type of cam. For a longer stroke, the two-pin steel cam must be used.
Tools Needed to Dial In (or Degree In) a Steel Billet Camshaft -
|
|
|
"
"Dial Indicator"
"Piston
Stop"
Check your local automotive parts supply stores for a dial indicator and degree wheel. If they don't have them in stock, they can probably order them for you. eBay is also a good place to find these items. But a piston stop will probably have to be fabricated from scratch, because they're not marketed for single cylinder engines. Or for a piston stop, on a flathead engine, a long reach spark plug can be used, and the cylinder head can be positioned it so the spark plug is over the piston.
Advancing or Retarding the Steel Camshaft: (The paragraph below was copied and pasted from Vogel Manufacturing.)
Adjust at the gear (loosen the (4) four clamping bolts) by moving approximately 5° in either direction. To return to position as ground, line up the ¼" dowell hole in gear with the ¼" dowell hole in cam face and insert ¼" dowel. As a reference point, .020" movement at the cam flange O.D. is 1° cam movement or 2° crank movement. Remember, degree in a camshaft with no lash and no installed springs.
Failure to accurately degree in the camshaft can effect how an engine performs. Proper valve timing quickly becomes a crap shoot without a degree wheel. Published valve timing is only a suggested starting point based on dyno testing and track experience. There are variables that may call for different valve timing in your specific combination. If you don't know where your valve timing is then the cam grinder or engine builder cannot recommend changes to help you get the most out of your engine.
Now is a good time to mention that while your cam grinder or engine builder should be able to supply you with a cam appropriate for your application, it will be necessary in most cases to change jetting and fine tune the cam timing and lash settings to the operator's preference and ability. The cam grinder or engine builder cannot know about the rpm ranges in your application without good accurate information on which to base his recommendations.
There are two easy ways to change the characteristics of your cam. Advancing and retarding the cam can move the power band up or down a few hundred rpm. Advance for more bottom end and retard for more top end. It usually takes about a 4° change to feel it. The second way is to change the valve lash. Tightening the lash will increase the top end power while loosening it will increase bottom end power. You won't hurt anything by tightening the lash but check with your cam grinder as to the maximum lash you can use before running off the ramp and damaging the valves. When making these changes, increases at one end mean decreases at the other end.
Valve opening and closing times are measured by the number of degrees of crankshaft rotation that takes place before or after what is called the piston's Top Dead Center (TDC) or Bottom Dead Center (BDC) positions. A piston is at TDC when it is at its highest point in the cylinder and at BDC when at its lowest point. The intake valve opens before the piston reaches TDC (which is BTDC) on the exhaust stroke and closes after the piston passes BDC (which is After Top Dead Center or ABDC) on the intake stroke. While the exhaust valve opens before the piston reaches BDC (BBDC) on the power stroke, it closes after the piston passes TDC (ATDC) on the exhaust stroke.
Names of Different Areas of the Cam Lobes
To find how much lift any particular cam has, using a micrometer or dial caliper, measure across the base circle of one lobe and then measure from the base circle to the toe of the same lobe, and then divide the difference. The answer will be the amount of lift each lobe has.
Go here for Vogel's CAMSHAFT AND VALVETRAIN INFORMATION. (.PDF file.)
How to Dial In (or Degree In) a Steel Billet Cam for a Kohler Engine -
-
Use a pencil, paper and arithmetic for this procedure, to keep track of the
results.
-
Install the valves, lifters, camshaft, crankshaft and front bearing plate
in the engine. Make sure that the timing marks on both the cam gear and the
crank gear are aligned. With the piston on the compression stroke and both
valves fully closed, set the valve lash at zero for both valves. Install
some stock valve springs to ensure that the valves will be in the fully closed
position, and for a more accurate reading. Make sure the ends of the lifters
and valve stems are ground square for proper adjustment!
NOTE: If there's no timing or alignment marks on the gear teeth on the engine you're reassembling, then the to align or time the camshaft with the crankshaft is with the piston positioned at TDC and both lobes on the cam at BDC or pointing downward. Then, install the valves in the block. Rotate the crankshaft until the piston is at TDC on the compression stroke. The valves should be fully closed. If the piston is on the exhaust stroke at TDC, each valve should be open slightly. And if you "rock" the piston up and down slightly with it on the exhaust stroke, one valve should close and the other should slightly open and vice-versa. - Fashion a rigid pointer from stiff wire or an old coat hanger and attach it to the engine block. This pointer locates the degrees on the degree wheel.
- With the degree wheel installed on the flywheel end of the crankshaft, rotate the crank to get the piston at TDC and check to ensure that the valves are fully closed then adjust the pointer to zero (0º TDC) on the degree wheel.
- Turn the crankshaft opposite the running rotation approximately 15-20°. Install a piston stop on the top of the engine block fastened in place by two head bolts.
- Continue to turn the engine in the same direction until the piston comes back up and just touches the piston stop. Make a note of the exact number on the degree wheel that the pointer is on.
- Rotate the engine in the other direction (running rotation) until the piston comes back up and touches the piston stop. Again note the number where the pointer is.
- Remove the piston stop and rotate the crankshaft to the midpoint of the two marks. At this point the piston is at the true top dead center. Loosen the degree wheel and adjust it so it will read 0º TDC at the pointer. Don't rotate the crankshaft to do this!
- Now, it's time to locate the lobe centerline relative to TDC. Attach the dial indicator's magnetic base on the top of the engine block. Set the tip to contact the top of the intake valve. Check to make sure that the indicator plunger is parallel to the valve stem. NOTE - any variance in an angle will produce geometric errors in the lift readings.
- Rotate the crankshaft in the normal direction (the direction in which the engine cranks over to start it) until maximum lift of the intake lobe on the cam is reached. Maximum lift is attained when the dial indicator starts to change direction. At this point reset the dial indicator to zero.
- Now turn the crankshaft in the normal direction until the indicator reads .050" before maximum lift. Make a note of the number on the degree wheel.
- After that reading, continue to rotate the crankshaft in its normal direction until the indicator goes past its zero setting to .050" on the closing side of maximum lift. Again, record the reading.
- Add the two numbers and divide the answer by two. This number is the location of maximum lift of the intake lobe relative to the crank and piston (a.k.a. the intake centerline). Check the cam spec card and it should confirm the settings. If it doesn't, remove or install end-play shims or adjust the cam gear as necessary.
By the way, I wish the people who custom grind and sell high-performance adjustable steel cams would include detailed instructions in their packages on how to set the cam timing. It's not right for me to have to try to explain it to everyone. Because I'm not making any money off any of my pulling tips.
See this web site for additional information for degreeing in a single cylinder engine camshaft: http://www.compgoparts.com/Support/Tutorials/CamshaftDegreeing.asp
How the Automatic Compression Release (ACR) Mechanism Operates -
The ACR mechanism consists
of two flyweights and a spring attached to the gear on the camshaft. When
the engine is rotating at low cranking speeds (600 rpm or lower), the flyweights
are held inward by a small spring in the position shown in the 1st drawing
to the right, resulting in an effective compression ratio of about 2:1 during
cranking.
After the engine speed increases above 600 rpm, centrifugal force moves the flyweights outward (in the position shown in the 2nd drawing to the right). In this position, the tab on the larger flyweight drops into a recess in the exhaust cam lobe. When in the recess, the tab has no effect on the exhaust valve and the engine operates at full compression to produce full power.
Performing a Compression Test on an Air-Cooled Gas Engine -
The compression relief is a
mechanical swing arm on the cam. At cranking speeds, it holds the exhaust
valve open about .050" to relief about half the compression so the engine
will start easier. Because no engine can start under full compression with
advanced ignition timing. When the engine starts, the increased rpm or
centrifugal weight opens the swing arm so the exhaust valve will have 100%
contact with the seat, allowing the engine to run under full compression.
The compression relief mechanism on the camshaft relieves about half of the compression pressure in the combustion chamber at cranking speeds. When the engine starts, the compression builds up to 100%. On OEM camshafts with a working compression relief mechanism and if the valves are adjusted to specs, the compression relief relieves about half the compression from the combustion chamber at cranking speeds. So when performing a compression test (with a gauge) on an air-cooled engine, keep in mind that, depending on how the engine is built, the compression ratio or the compression pressure can vary a lot from one engine to another. It depends on the size of the bore and stroke, if the head is milled flat or milled out for high lift valve clearance, if the camshaft has a compression relief or not, how much duration the cam has and the valve head diameters. When performing a compression test on a 10hp Kohler engine, it can range anywhere from 98 to 150 psi. On a 12hp, it can be from 112 to 170 psi. On a 14hp, it can range from 120 to 190 psi. And on a 16hp, it can be from 127 up to 192 psi. But as an engine wears, the compression will become less.
And cranking speeds, a long duration cam will relieve some of the combustion chamber pressure, resulting in a lower than normal reading. The more the duration, the lower the reading. To obtain an accurate compression pressure reading, perform the test with a fully charged battery and the throttle in the wide open position. Now perform the test. Then calculate the reading with the duration of the cam in the engine against the duration of a stock OEM cam. Example: If the compression pressure is 100 psi, I multiple 100 by 285 (duration of cam that's in the engine) and then I divide the answer by 223° (duration of a stock OEM cam), which gives me 128 psi. And if a cam has a compression relief mechanism, the compression reading will be cut in half.
NOTE - Cam technology is always improving! What works for one engine won't necessarily work for another. Therefore, if you're wondering which cam profile will work best for your particular engine, it really depends on how many rpm the engine is going to turn. If it's going be governed at 4,000 rpm, then perhaps an 18hp OHV cam will work fine. But if it's going to turn faster, then a cam that's designed for a Stock-Altered or Super-Stock engine should be used. It's best to talk to a professional cam grinder person to determine which cam would benefit your engine best so it'll produce maximum rpm, power and torque. Professional engine builders are the ones that really should answer your questions about choosing the correct cam for your particular engine. If you're looking for a quality cam for your garden pulling tractor, or wondering which grind to use in your engine, contact Lakota Racing (http://www.lakotaracing.com) Midwest Super Cub (http://www.midwestsupercub.net), Vogel Manufacturing Company (http://www.vogelmanufacturing.com) or look in my advertisement web site or you can place a want ad in the same site for a cam.
For one of the best camshaft grinders around, fast and able to talk to all the time, contact Greg Hackman of Small Engines in Seymour, 726 E. Tipton St., Seymour, Indiana. Phone 1-812-522-4777. All of the top NQS engine builders use these cams. They are great people to talk to and are really knowledgeable about camshafts.
Exhaust Header Pipe - Top of page
If
you've ever had an engine with a stubborn or rusted exhaust elbow pipe fitting
that's threaded-in-the-block, then you probably already know how much of
a pain it is to remove. Well, this is how to remove the fitting if enough
of it is protruding from the exhaust port:
- Apply penetrating oil to the pipe fitting threads and exhaust port. Gunk's Liquid Wrench works great for this!
- Clamp the engine block in a hydraulic press or place it under a heavy vehicle. (Only to hold it in place.)
- Use a large adjustable plumber's pipe wrench to remove the fitting. Rotate it counter-clockwise to loosen it. If the pipe wrench alone won't loosen it, slide a 3 foot long steel tubing on the pipe wrench's handle for added leverage. And don't worry, if done correctly, the block won't crack or break when loosening the fitting.
- If the fitting breaks off flush with the block, then it will need to be chiseled out to collapse the threads. Chisel only where the metal is thick in the block, to avoid breaking the exhaust port!
- After the fitting is removed, clean and straighten the threads with an NPT tap. A new pipe can now be installed. Or, if you're going to build an engine for pulling competition, install a professional header pipe as shown below.
The two
holes that's to be drilled and tapped for the header pipe in the exhaust
port of the engine block should be performed on the table of a large milling
machine by an experienced machinist. The holes are to be drilled with a letter
"F" or 17/16" drill bit, and about 1-1/4" deep. Then the threads cut
perpendicular to the exhaust flange with a 5/16-24 NC tapered tap. Use plenty
of oil and go slow to prevent from breaking the tap off in the block. Because
if it breaks off, it'll be extremely hard to remove!
Advertisement:
| If you need a complete exhaust header pipe kit that's ready
to bolt on, please contact A-1 Miller's Performance Enterprises | 1501 W.
Old Plank Rd. | Columbia, MO 65203-9136 USA |
Phone: 1-573-875-4033. Please
call Monday-Friday, 9am to 5pm, Central time. If no answer, please try again
later. (When speaking with Brian, please be patient because I stutter.)
Fax: 1-573-449-7347.
E-mail:
pullingtractor@aol.com. You can
also contact us through Yahoo! Messenger:
|
|
 Drill and tap
two 5/16"-18 holes in exhaust flange (to mount header pipe). $40.00
labor, plus return shipping & handling. |
|
Header pipe kit for 10hp, 12hp and 14hp Stock, Stock-Altered or 30 c.i. Super-Stock Kohler engines with stock size or oversize valves and with or without a governor lever.
Kit includes one 1-3/16" i.d. x 1-5/16" o.d. pipe; measures approximately 7" from the block and approximately 19" tall; has a 90°, 4" radius mandrel bend; mounting flange; two stainless steel Allen head (5/16-18 NC) mounting bolts and an anti-vibration brace. Galvanized-coated steel. Very shiny, resists rust and won't discolor from extreme exhaust heat. Designed for use on Cub Cadets and some other makes & models of garden tractors with a 10, 12 or 14hp Kohler K-series or Magnum engine. This pipe has a flange that securely fastens to the engine block with two furnished 5/16" diameter coarse thread Allen head bolts. If your block don't have the two threaded mounting holes, then they will need to be drilled and tapped to accept the flange. There is no other way to fasten this pipe to the block. Comes with no mounting gasket. Use silicone sealer instead. The flange is also small enough to clear the governor lever. Shipping weight is 4 lbs.
|
Header pipe kit for 16hp Stock, Stock-Altered or Super-Stock Kohler engines with stock size or oversize valves and with or without a governor lever.
Kit comes with a 1-3/8" i.d. x 1-1/2" o.d., pipe; measures approximately 7" from the block and approximately 19" tall; 90°, 4" radius bend; mounting flange; two hex head stainless steel mounting bolts with flat washers and an anti-vibration brace. 16 gauge galvanized-coated steel. Very shiny, resists rust and won't discolor from extreme exhaust heat. This pipe has a flange that securely fastens to the engine block with two furnished 5/16" diameter coarse thread (5/16-18 NC) bolts. Requires no adapter. If your block don't have the two threaded holes, then they will need to be drilled and tapped to accept this pipe. There is no other way to fasten this pipe to the block. Comes with no mounting gasket. Use silicone sealer instead. Designed for use on Cub Cadets and some other makes & models of garden tractors with a 16hp Kohler K-series or Magnum engines. Shipping weight is 4 lbs.
|
 Steel header pipe mounting
flange for 10, 12 and 14hp single cylinder, and KT17, KT19, M18 and M20 twin
cylinder Kohler and Magnum flathead engines. Approximately 3/16" thickness,
(2) 5/16" diameter mounting holes spaced 1-3/4" apart, 1-5/16" center hole.
Fastens directly to engine block. NOTE: Two 5/16-18 NC threaded holes
must be drilled and tapped in the exhaust port to accept this flange.
$10.00 each, plus shipping & handling.
5/16-18 NC stainless steel Allen head bolts for above flange.
$2.00/set of 2, plus shipping & handling.
|
 Steel header pipe mounting
flange-to-engine block for 16hp Kohler engines.1/4" thick, (2) 5/16" mounting
holes spaced 2-1/4" apart, 1-1/2" center hole. To be welded onto a 1-1/2"
o.d. pipe. Fits 16hp Kohler K-series and Magnum flathead engines and adapter
below. NOTE: Two 5/16-18 NC threaded holes must be tapped into exhaust
port to accept this flange. $15.00 each, plus shipping & handling.
|
 Steel header pipe mounting
flange-to-cylinder head for 18hp OHV K361 single cylinder Kohler engines.
1/4" thickness, (4) 5/16" diameter mounting holes spaced 1-1/32" apart, 1-1/2"
center hole. $20.00 each, plus shipping & handling.
5/16-18 NC stainless steel Allen head bolts for above flange.
$4.00/set of 4, plus shipping & handling.
|
 NOTE: Neither of the
header pipe kits above come with a clamp. To fasten the anti-vibration brace
to the pipe, with an engine turning no more than 4,000 rpm, it's safe to
use a stainless steel automotive radiator hose clamp. But if an engine is
going to run at
wide
open throttle, it's best to use a 1-1/2" automotive "U" shaped muffler
clamp. These are available at most auto parts store. By the way - the
anti-vibration brace is important to use because I think there's nothing
more embarrassing and being disqualified than having a welded-on header pipe
break off next to the weld while the tractor is pulling down the
track. |
5/16-18 NC stainless steel hex-head
bolts with flat washers for above flange. $2.00/set of 2, plus shipping
& handling.
Linked pages to our parts & services:
A-1 Miller's Performance
Enterprises |
Engine Rebuild Parts, Engine Rebuilds, Build-ups, Exhaust Header Pipe Kits & Machine Shop Services |
Transmission, Transaxle Parts, Rebuilds & Machine Shop Services |
|
Ignition, Electrical and Crank Trigger Electronic Ignition Parts and Kits |
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