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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 with 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 Grinding Compound (which is actually valve lapping compound), is not meant for "grinding valves". I realize it reads on the label: "Valve Grinding Compound," but this is wrong because it doesn't grind valves (or seats) whatsoever. A valve seat cutter/grinder and valve face grinding machine is meant to do this. The valve lapping compound is actually used to create a rough surface on the valve face and seat so they'll wear into each other as they break in, forming a perfect seal to keep the valves from leaking out 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...
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.
To do a lousy valve job, some people will just remove the valves, clean them thoroughly and then use valve grinding (lapping) compound to reseal them to the seats and then reset the valve clearances. Doing this will help an engine run better for a while, but it's not how to perform a professional valve job. The tools that's required to perform a professional valve job are as follows: valve spring compressor tool, valve face grinding machine, [Sioux] valve seat grinder or [Neway] valve seat cutter kit, valve grinding (lapping) compound and a valve lapping tool. There's also a valve guide removal/installation tool and a valve guide reamer, too. To do it right the first time and make the valves last longer so the engine will produce more power...
What Are Valve Rotators and Why Are They Used?
For a non-pulling engine, valve rotators help prevent valves from burning by rotating the valve slightly as it opens to scrape away any carbon deposits from the valve face and seat. If an engine didn't come with valve rotators (most early Kohler engines didn't), they can be installed instead of the stamped steel non-rotator retainers. Many automotive engines use valve rotators, too. A rotator should be used with the exhaust valve because that's the one where the carbon exits the combustion chamber, and is optional for use with the intake valve. Rotators can be used in any 6¼hp-16hp Kohler engine. It's important that a rotator be used with the 1-9/16" uncompressed height OEM valve spring to prevent coil bind at full valve lift, which may result in cam breakage. Stamped or machined steel retainers require a 1-3/4" uncompressed height OEM spring. If the shorter 1-9/16" spring is used with a non-rotator retainer, the valve(s) may float, and/or the keepers may become dislodged from the valve stem at higher rpms. Although valve rotators are extremely strong, competitive pulling engines don't require them because they don't run long enough for carbon to build up in the combustion chamber.
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 (except Holidays), 9am to 5pm, Central time zone. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: email@example.com. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest.|
|New Valves for
Kohler engine models KT90/KT91. These valves not available in
|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.
|Valves for Kohler
K-series and Magnum engine models K241/M10 (10hp), K301/M12 (12hp), K321/M14
(14hp) and K341/M16 (16hp) flatheads, and models K482, K532 and K582.
|New Valves for
Kohler K-series K361 (18hp OHV) cast iron block engine. Not available
|New Exhaust Valve
and Valve Kit for Kohler twin cylinder flathead models MV16, M18 and MV18
engines only. NOTE: New intake valves are no longer available for
models MV16, M18 and MV18. And new intake and exhaust valves for models KT17,
KT17II, KT19, KT19II, KT21, M20 and MV20 are also no longer available. If
they're not severely worn, warped or burnt, the original intake (and exhaust)
valves can be reground and reused. And if they're bent, they may be
|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.
|Valve Guide Removal and Installation Tool. Use with a big hammer to remove (drive out) and install valve guides. Can be used for OEM Kohler and aftermarket offset valve guides. Machined from 1/2" diameter x 5" overall length grade 8 bolt. .300" diameter pilot. $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. Provides proper clearance. Will not allow
the valve stems to be too loose or too tight.
|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
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.
| 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. Can be used with high performance valve
spring below. Briggs & Stratton part # 494553; Kohler part # 41 755 10-S.
|OEM Kohler Valve Spring Retainers and Rotators. Fits 5/16"
diameter valve stems. Fits Kohler K-series and Magnum K141, K160/K161, K181/M8,
K241/M10 (10hp), K301/M12 (12hp), K321/M14 (14hp), K341/M16 (16hp), K361
(18hp OHV), K482, K532, K582 and twin cylinder KT series and Magnum flathead
engines. Rotator only also fits 6hp-18hp single and twin cylinder Briggs
and Stratton exhaust valves.
| OEM 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 with cam having stock lift. NOTE: Used
OEM valve springs rarely lose their pressure. They can be reused as long
as they're not pitted with rust, which makes a weak spot and could cause
them to break over time.
OEM 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.
Hot-Stock and Stock-Altered High Performance Single Valve Springs for Kohler K-series and Magnum K241/M10 (10hp), K301/M12 (12hp), K321/M14 (14hp), K341/M16 (16hp) and K361 (18hp OHV). Designed for cams up to .400" lift in engines that run at high rpms or at wide open throttle. Can be used with OEM Kohler stamped steel/non-rotator retainers and keepers. (OEM rotators may cause coil bind, resulting in cam breakage.) Dimensions: .953" i.d.; .697" o.d.; 2" uncompressed height. Specifications: Seat load: 55 @ 1.500"; Open load: 127 @ 1.000"; Coil bind: .950"; Spring rate (lbs/inch): 144.
|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.
|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.|
|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.|
Below is the professional way of doing it.
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.
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. This also happens with certain OHV (OverHead Valve) small engine (and certain automotive) cylinder heads. But on the K361 head, 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) or loose in it's bore, it will need to be repaired first.
How to Repair a Loose Valve Seat:
|If you need your K361 cylinder head repaired or parts, 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 (except Holidays), 9am to 5pm,
Central time zone. If no answer, please try again later. (When speaking
with Brian, please be patient because I stutter.)
firstname.lastname@example.org. You can
also contact us through Yahoo! Messenger:
Find us here:
Directions to our shop |
Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO |
1501 West Old Plank Road, Columbia, MO - Google Maps or
Map of 1501 West Old Plank
Road, Columbia, MO by MapQuest.
Kohler model K361 (18hp OHV) Cylinder Head Repairs - NOTE: I have another automotive machine shop here in Columbia repair my customer's K361 heads because I don't have the required equipment and tooling to perform the repairs. Sometimes they get busy with a lot of other customer's repairs and if you want to send your head to me, it may be some time before they will have it repaired. I can't say when they will have it repaired, but they perform professional, high quality work & they guarantee their repairs.
Complete engine rebuild gasket set w/oil seals for Kohler K-series model K361 (18hp) cast iron block single cylinder OHV engine. Includes oil seals. (The aftermarket set is actually less than individual OEM gaskets just to reinstall the head.) Kohler part # 45 755 06-S.
New Valves for Kohler model K361 (18hp OHV) cylinder head. These valves not available in aftermarket.
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 25-30% bigger than the exhaust valve, which would make it 1.68". And this is way too big for the K361 head.
|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 (except Holidays), 9am to 5pm, Central time zone. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: email@example.com. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest.|
|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
Other Services include:
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 grinding (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:
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".
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. For more higher rpms or at wide open throttle, the intake valve needs to be 25-30% bigger than the exhaust valve. 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. Most K-series intake valves are made of mild steel, and all Magnum intake (and exhaust) valves are made of extremely hardened steel (Stellite). 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.
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.
The Reason Most Small Engines Use Low-Pressure Valve Springs Opposed to Much Stiffer Automotive Springs -
Most 4-cycle flathead and OHV lawn and garden equipment small engines have a governor that controls and limits the engine's top speed and allows the engine to rev to around 3,200-3,600 rpms. The valve springs don't need to be very stiff at 3,200-3,600 rpms because the engine doesn't rev fast enough for... 1) the valves to float, and 2) the keepers to become dislodged, causing a valve to disconnect from the retainer. In an OHV engine, this is known as "dropping a valve." Which will likely destroy the engine. For most automotive engines on the other hand, they don't use a governor to limit the engine's rpms. Therefore, they require much stiffer valve springs, especially the OHV engines, so the engine will rev up faster, and to lessen the chance of "dropping a valve."
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.
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.
There are two ways to measure the amount of wear in valve guides. One way is with a dial indicator. The other way is with an "go/no go gauge" and a micrometer. It's best to have a local machine shop do the measuring because they have the right tools and they're experienced with such things.
How to Remove and Install Pressed-In Cast Iron Valve Guides in a Cast Iron Block Kohler Engine:
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:
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.
|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 (except Holidays), 9am to 5pm, Central time zone. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: firstname.lastname@example.org. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. Go here for more parts: Carburetor, Fuel System Parts & Machine Shop Services|
|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...
How to check for proper valve clearance between the valves and cylinder head...
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.
"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 ports are made smooth. Many years ago, most high performance engine builders thought that by making the intake port and intake manifold (or carburetor extension, spacer, intake tube, stand-off, or whatever they may be called by garden tractor pullers), smooth and polished, this would help the engine to produce more power and torque. Which in theory makes sense. But in reality and in recent dyno tests, the intake passageway shouldn't be smooth or polished. If enlarged (for more airflow), but made with a rough surface, this will create turbulence in the port. The turbulence will cause the incoming air to atomize with the fuel vapors more thoroughly, which will help the engine produce much more horsepower and torque at high rpms or at wide open throttle. The exhaust port and header on the other hand, should be smooth and polished, so the spent exhaust gases can exit the combustion chamber quickly.
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 (Tappets) -
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.
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:
The camshaft is the heart of an engine. 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." Cams with much more lift and duration than a stock or low rpm torque cam is considered a "big cam."
How a high performance cam with more lift and a lot of duration works -
Air is very flexible. It can be compressed as well as it can be expanded. When an engine has a long duration cam, with the cylinder head off, as the crankshaft is slowly rotated by hand, you may notice that before the piston reaches TDC (Top Dead Center) or BDC (Bottom Dead Center), the valves stay open longer and doesn't fully close until the piston is a good ways up or down in the cylinder. This is called "duration." With an OEM stock cam or short duration cam, the valves will become fully closed when the piston is at or close to TDC or BDC. Anyway, with a long duration cam, when an engine revs at high rpms or at wide open throttle, air doesn't have time to exit out through the valves, so it "compresses" and becomes trapped within the combustion chamber. In this way, the piston can draw more air (and fuel mixture) into the combustion chamber through the intake valve. The engine is able to build up more compression at higher rpms with a long duration cam so it will produce more power. In addition, a larger portion of the burned gases will be expelled from the combustion chamber through the exhaust valve. This is why most high performance automotive engines with a long duration cam idle "radically" or with a low tone, loping sound, and single cylinder pulling engines have that "boom, boom" sound out the exhaust with an open header pipe. That's air the piston is pushing out past the exhaust valve before the valve can fully close at a high rate of speed, creating a small sonic boom. The reason it makes a loud sound is because the air is moving faster than the speed of sound, which breaks the sound barrier.
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 the 1.280" diameter wide base lifters with a cam that has at least .400" of lift despite the 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 isnít 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.
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, Amsoil 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.
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.
These cams have the same lift and duration as the newer ones with the compression release, and the other difference are as follows:
They don't have a compression release.
It takes more effort to crank an engine with these cams.
The ignition timing sets at 0° TDC instead of 20° BTDC.
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. By the way - I've always preferred clear RTV silicone adhesive sealant for two reasons: it bonds parts together, forming a leak-proof seal; and being it's clear, it makes for a clean-looking repair job. It can't be seen between the parts.
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.
|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 (except Holidays), 9am to 5pm, Central time zone. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: email@example.com. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest.|
|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.
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 Kohler K-series and Magnum engine models K241/M10 (10hp), K301/M12 (12hp), K321/M14 (14hp), K341/M16 (16hp) and K361 (18hp OHV). This cam profile has stock lift with increased duration and will pass tech for an OEM Kohler stock cam. 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. This cam performs best with reworked and undercut valves for more airflow, ports made larger and the venturi in the carburetor bored out. If there's any restriction in and out of the combustion chamber, the cam will not be able to perform at 100% efficiency. This cam profile helps the engine produce the most power and torque between 3,600-4,500 rpms. At higher rpms, no substantial increase in power will result. 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. Use with stock lifters. 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!
FYI: When the cam lobes are reground, metal is removed from the base circle which reduce 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 grinding machine's grinding stones are about 1" wide, and after the cam grinding process, I have to manually 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. Otherwise, if everything else is set up correctly with your engine, this cam should work fine. There's no need to be concerned when you receive the cam and see the metal ground away. Also, some of the cams I have, the points lobe is slightly worn. (It's hard to find a good used, 100% unworn cam nowadays.) 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.
Hot-Stock and Stock-Altered Camshaft for Kohler K-series and Magnum engine models K241/M10 (10hp), K301/M12 (12hp), K321/M14 (14hp), K341/M16 (16hp) and K361 (18hp OHV) Pulling Engines. Lobes are hard surface welded on an OEM cast cam, then precision ground to give it a stock lift (.325"-.330"), but much more duration. This cam profile performs best with reworked and undercut stock size valves or bigger valves for more airflow, ports made larger and the venturi in the carburetor bored out. If there's any restriction in and out of the combustion chamber, the cam will not be able to perform at 100% efficiency. This cam profile helps the engine produce the most power and torque at high rpms or at wide open throttle operation. If used in a 4,000± rpm engine, no substantial increase in power will result. Single, Stock-Altered springs required for this cam. Stock OEM Kohler 1" base lifters can be used.
|Replace worn lifters to prevent erratic valve action and
premature cam lobe wear -
Valve Lifter (Tappet) for Kohler K-series and Magnum single cylinder flathead engine models K141 (6¼hp), K160 (6.6hp), K161 (7hp) and K181/M8 (8hp). Length: 1.964" for exhaust valve only and camshaft with automatic compression release (ACR). OEM Kohler part # 230013-S. Grind end of valve stems to set valve clearances.
Valve Lifter (Tappet) for Kohler K-series and Magnum single cylinder flathead engine models K141 (6¼hp), K160 (6.6hp), K161 (7hp) and K181/M8 (8hp). Length: 2.020" for intake and exhaust valves and older two-piece camshaft without automatic compression release. OEM Kohler part # 232777-S. Grind end of valve stems to set valve clearances.
1" Width Base Adjustable Valve Lifter (Tappet) for Kohler K-series and Magnum single cylinder flathead engine models K241/M10 (10hp), K301/M12 (12hp), K231/M14 (14hp) and K341/M16 (16hp). Use for OEM stock or performance cams with up to .340" lift. OEM Kohler part # D-235327-S.
1.280" Width Base Adjustable Valve Lifter (Tappet) for Kohler K-series and Magnum single cylinder flathead engine models K241/M10 (10hp), K301/M12 (12hp), K231/M14 (14hp) and K341/M16 (16hp). For high performance cams with .400"-.575" lift.
Compression Release Actuating Spring for Kohler K-series and Magnum single
cylinder engine models K181/M8 (8hp), K241/M10 (10hp), K301/M12 (12hp), K231/M14
(14hp) and K341/M16 (16hp). OEM Kohler part # 47 089 01-S.
Pins for Kohler Cast Iron Block Engines.
|Camshaft End Thrust
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 cast iron camshaft that originally came in the Kohler model K361 18hp OHV engine is no longer available from Kohler. If you're lucky, you might find a new cam from old stock. The part number for this cam is 45 010 05S. They fit the 12, 14, 16hp flathead engines, too. Good for up to 4,000 rpm.) They work great in a stock engine!
18hp cam works great for increased power in a 10hp and 12hp engines, but
it won't do quite as much in the 14hp and 16hp engine because of more cubic
inches. 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.
If you have a cam that was broke in two by a thrown connecting rod, save the tiny (hair-like) actuating spring from the compression release mechanism. It can be used on another cam that may not have one.
|Camshaft||OEM Kohler 10hp, 12hp, 14hp & 16hp Flathead Cams (Average)||OEM Kohler 18hp OHV Cam||Reground 4,000 rpm Torque Cam|
|Exhaust Opens, Degrees BBDC||50°||50°||60°|
|Exhaust Closes, Degrees ATDC||20°||25°||36°|
|Intake Opens, Degrees BTDC||30°||52°||40°|
|Intake Closes, Degrees ABDC||70°||79°||80°|
|Exhaust Duration, Degrees||250°||255°||276°|
|Intake Duration, Degrees||280°||311°||300°|
|Maximum Lift, Exhaust||.301"||.306"||.311"|
|Maximum Lift, Intake||.308"||.325"||.317"|
|Recommended Lash Settings|
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. By the way - I've always preferred clear RTV silicone adhesive sealant for two reasons: it bonds parts together, forming a leak-proof seal; and being it's clear, it makes for a clean-looking repair job. It can't be seen between the parts.
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 flat bar type of piston stop tool.
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 Billet Steel Camshaft -
The degree wheel is a round disc (usually made of aluminum) with the facing edge marked off in degrees, similar to the markings on a protractor. When used in conjunction with a dial indicator, it's installed on the crankshaft during the engine build to degree the cam in and check for correct valve timing events. It can also be used to check for accurate ignition timing. When in use, a degree wheel is fastened to the front of the crankshaft (automotive engines) or flywheel end (small engines). If it's fastened to the PTO end, it will need to face the engine block and be read from that position. Degree wheels can be purchased off of eBay.
Dial Indicator and Magnetic Base
A dial indicator is necessary to check for correct valve timing to tell precisely when a valve starts to open and the moment it closes. This opening and closing is very critical for high performance engines and cannot be done by feel or by sight. A dial indicator can also be used to set accurate ignition timing in relation to piston travel. Each mark on the face of a dial indicator represents one thousandth of an inch (.001") graduations. The marks with a number (10, 20, 30, etc.) represents every ten thousandths of an inch (.010", .020", .030", etc.). A dial indicator always mounts on top of the engine block. Dial indicators are very precision and delicate instruments. Care must be used in handling one. Dial indicators can be purchased from LittleMachineShop.com.
Piston Stop Tool
A piston stop tool is used to accurately find the piston's true Top Dead Center (TDC). For a multi-cylinder engine, the piston stop is always used on the #1 piston, which is closest to the front of the engine block.
To make a simple piston stop for a flathead engine, if the spark plug is perpendicular with the head, an old, long-reach (long threaded) spark plug can be used in the head for a bump-stop. Simply position and fasten the head on the block with the plug directly over the piston. The spark plug can be adjusted up or down to find the top dead center of the piston in relationship with the degree wheel. A steel rod may need to be welded on the end of the plug for an extended reach.
Or for a universal flat bar type of piston stop, the bracket part should be made of minimum 1/4" thick x 1" wide flat steel or aluminum, drilled with a couple of holes so that it can be fastened to the top of the block with a couple of head bolts, directly over the piston. A minimum 1/4" bolt with a jam nut, threaded upside-down into the bracket is also required. The adjustment of the bolt is used to "stop" the piston. If a piston pops out of the cylinder at TDC, then to use a piston stop, install several spacers (flat washers) between the piston stop and engine block so the bracket will clear the piston and go past the TDC mark.
Advancing or Retarding a Steel Camshaft with an Adjustable Gear: (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.
How to Dial In (or Degree In) a Steel Billet Cam for a Kohler Engine -
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.
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:
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!
|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 (except Holidays), 9am to 5pm, Central time zone. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: firstname.lastname@example.org. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest.|
|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 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.
5/16-18 NC stainless steel hex-head bolts with flat washers for above flange. $2.00/set of 2, 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 Allen head bolts for above flange. $4.00/set of 4, plus shipping & handling.
|Heavy Duty Header Pipe U-Bolt Clamps. Available for our 1-5/16" header and 1-1/2" header pipes. $2.50 each, plus shipping & handling.|
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