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  #1  
Old 06-13-2013, 03:21 AM
machinehead323 machinehead323 is offline
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Default correct way to do a valve job?

well im looking for some info from those here that have done it. i have never messed with the valves before. im regrinding me seats and installing new kohler stellite valves that were spec'ed for my k341 in my 1650. the info below is from brian millers website. i am keeping the 45 degree angle as spec'ed. its seems like below he installed the valves without lapping them, then after a couple hour they seat in. then later on he talks about lapping the the valves at the end. im sure i, reading his writeup wrong. i wouldnt think he put it together ran it then lapped em in. just looking for the right way to do it.

from another website. http://************************.com/valvecam.htm
First rotate the crankshaft until the piston is at top dead center (TDC) on the compression stroke. Or, rotate the camshaft (if the crank is out of the block) until both valves are fully closed. If it's a twin cylinder engine, do this for each cylinder.
After removing the crankcase breather, remove the valves using a valve spring compressor tool. Be sure not to lose the keepers! Store the valve components in a container so nothing will be misplaced! If you don't have a valve spring compressor tool, two medium size flat screwdrivers can be used to compress the spring and then have someone else remove and install the keepers. I had to do this when I first started working on engines. Then I found that a valve spring compressor makes it a lot easier.
Remove the valves, clean all the parts, and use a wire wheel to clean the carbon from the valves. They may need to be sandblasted if the carbon is really hard to remove.
Inspect the valve face for wear, and measure the stem diameter for wear.
Check the valve guides for wear. Most of the time, the exhaust guide will wear more than the intake due to carbon deposits. The maximum wear limit on the 7hp and 8hp Kohler engines is .005" for the intake,.007" for the exhaust. And on the 10hp, 12hp, 14hp and 16hp Kohler engines, it's .006" for the intake and .008" for the exhaust. If the guides are worn, install new guides or have a new thin-wall bronze liner installed. An excessively worn intake and/or exhaust valve guide will cause an engine to make a popping sound out the intake or exhaust while it is running.
If they're not burnt, bent or badly warped, then used valves can be refaced on a valve grinding machine at an automotive engine machine shop. But if they're damaged or excessively worn in any way, they must be replaced. If the valves are reusable, grind the intake and exhaust valve(s) and seat(s) at 45º/46º angles (Kohler engines), respectively. The reason there's a 1º difference is because as the valve and seat wear together, they'll form a perfect 31-½° angle (intake, for high performance use) or 45-½° angle (intake and exhaust) leak-proof seal. As the valves/seats break-in, the engine will produce slightly more power because they'll be retaining full compression within the combustion chamber. In an average engine, it takes about 2 hours of operation for the valves to fully seat. When dyno-testing an engine, make sure it has at least 2 hours of break-in time on it.
NOTE: All of Kohler's valves come from the factory with a 45º angle, and the seats are ground at 46º. And there's no need for the valve seat contact area to be in the center of the face of the valve. (This is determined by lapping in the valves.) The engine will actually breath better at higher rpm if the seat contact area is towards the edge of the valve face.
After grinding the valves and seats, and with the governor assembly, lifters, camshaft, crankshaft, piston/rod and bearing plate all properly installed, and with the piston at TDC on the compression stroke (this when the base circle of the cam lobes are on top and both valves are fully closed), install the valves, springs, retainers and keepers and then check for proper valve lash (the clearance or gap between the valve stem and lifter). Set the valve clearances as follows for Kohler's K-series and Magnum single cylinder engines:
Always set the valve clearance when an engine is cold. Because metal expands when hot and shrinks when cold. On a fresh valve job, set the clearance on the maximum specs to allow for the valve face and seat to wear into each other. And then after approximately 25 hours of running time, recheck the clearances and set them at on the minimum. (If the gap haven't already minimized.)
For the 7hp and 8hp engines, the clearances are: .006"-.008" for the intake and .017"- .019" for the exhaust. Adjustment is made by lightly grinding the end of the valve stems. Be careful not to grind too much! This is the same way Briggs & Stratton and Tecumseh flathead engines valves are adjusted.
Use steel feeler gauges to set the valve clearances. For the 10-16hp engines, for ordinary yard use, the valve clearances are: .008"-.010" for the intake and .017"-.019" for the exhaust with the piston at TDC on the compression stroke. This is when both valves are fully closed. For competitive pulling, set the valve clearances at .010" for the intake and .014" for the exhaust.
When checking the valve lash on any engine, the piston in the cylinder for the valves that you're checking (on multiple cylinder engines) must be at top dead center (TDC) on the compression stroke. This places the lifters on the base circle of the cam lobes. The reason there's a valve lash is so the valves can fully close, sealing in the compressed air/fuel mixture in the combustion chamber. Too little lash, and some of the compression will escape through one or both valves, and in over time, a valve may burn. Too much lash, and the valves won't open fully, preventing the engine from producing full power.
To adjust the valves, remove the valve cover, and then rotate the crankshaft by hand until both valves are fully closed with the piston at TDC on the compression stroke. If one valve opens slightly and the other closes slightly and vice-versa while rotating the crankshaft back and forth, then the piston is on the exhaust stroke and the crankshaft needs to be rotated one full turn (180°). This will guarantee that both valves are fully closed so accurate valve adjustments can be made.
Valve adjustment is made with the engine cold, with a flat feeler gauge and on the 10-16hp engines, with the lifter held in place with a slender 1/2" open-end wrench and turning the adjuster screw in the lifter with a 7/16" open-end wrench. When checking valve clearance, always have the piston at the TDC position on the compression stroke. And make sure the ends of the lifters and valve stems are ground square for proper adjustment.
After making the proper lash adjustments, remove the valves, and apply a small quantity of valve lapping compound (available at most auto parts stores) on each valve face and then use a valve lapping tool (also available at most auto parts stores) to lap the valves in the seats (rotate each valve back and forth with the tool) until the "grinding sound" goes away. This process is important. It seals the valves in the seats.
After lapping in the valves, remove the valves and thoroughly clean the compound material from the valves and seats and then inspect the valve faces to see if the compound made full contact of 360º around each valve face and seat. If it didn't, then the valve is warped, or the face or seat wasn't ground correctly and will need to be re-done.
When installing the valves, lubricate the stems with motor oil. After compressing a valve spring, apply a small quantity of grease (chassis lub) on each keeper and on the end of a flat screwdriver, and then place the keeper on the screwdriver and use the screwdriver to place the keeper on the stem. (The grease will hold the keepers to the stem until the spring can be released.)
Rotate the crankshaft and observe the opening and closing of each valve. And take notice that the springs don't coil-bind. (Coil-bind is when the coils of the spring actually touch each other when the cam is at full lift. This may happen only with a high-lift cam.) If the springs do coil-bind, it may be necessary to remove the springs and grind some of the end off of each spring or acquire a different set of springs.
Reinstall the crankcase breather using new gaskets, and that's it!
__________________
1979 1650, #1 tiller with one extension, 90 degree box mounted, 3 point. 1961 4 digit bringing back to life. I have the mower and 3 pint for it. The 1650 is the fastest mower in the neighborhood.
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  #2  
Old 06-13-2013, 08:01 AM
dvogtvpe's Avatar
dvogtvpe dvogtvpe is offline
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since you are not using it as a puller after grinding the seat with the 46 deg stone I would use a 15 deg stone and lightly tap the top of the seat. this will create a more distinct contact area for a better seal. you then want the contact area more towards the center of the seat on the valve. this prevents burning the valve. if the contact area is to close to the top of the valve it can create hot spots for detonation since that area of the valve is pretty thin.
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