How-To: Valve Lapping



vandynamics

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#1
So i decided to take my gsr head and send it to a machine shop and have it hot tanked and have the valves bead blasted to remove all of the carbon. next step is valve lapping to ensure perfect compression across the board.

i suggest lapping the valves with everything removed. the valve spring, retainers, keepers, seats, and stem seals.

here is the head that is about to get the treatment. im starting with cylinder # 1 (closest to the cam gears)


here is the compound i am using for the lapping. its a single grit compound that you can pick up at a local NAPA for 6 dollars a load. some people using multi-grit compound. either are perfectly fine.




here is what the valve should look like with the proper amount of compound installed. as you can tell this isnt really brain surgery so theres no need to worry about over "compounding" the valve. when in doubt, apply more because you dont want to lap the valve dry.


here is the tools of the trade. a valve stem from a wheel rim (just stop by any tire shop near you and a mechanic will hand you acouple for free) and an electric drill:




here is the trickiest part of the seemingly simple process. spin the valve stem on the face of the valve. the friction will spin the valve and therefor lap the valve into the head. to assist the valve in spinning you should reach under the head with a tower and push up on the tip of the valve to lift it up from the head. this will assist in spinning the valve incase there is too much friction from the valve sitting in the head. again, a very easy process:


perfectly lapped valve:


perfectly lapped #1 combustion chamber:
 


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stealthy

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#2
could you explain what lapping does, when its necessary and how it helps? good write up=)
 

quicksilver1689

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#3
Hell yeah cor getting ur head ready for that cr frakenstein build. Good to see your doing everything the right way instead of just slapping it all together in one night and calling it done. props bro/
The valve lapping process is to insure that the valve seats perfectly when it closes. It makes sure the surfaces are smooth so it has a perfect mating surface.
 


vandynamics

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#4
ontop of almost perfect compression, it ensures that the valves cool down better. the valves are the hottest part of any given motor. the more surface/effective contact there is with the valve and the head (while the valve is closed) the better the cooling efficiency
 

stealthy

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#5
great great thanks!
 




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