Piston to valve clearance

ChuckZZ

Member
Building a stock stroke animal. Have a set of 1.30 roller rockers and a 308 adjustable cam. What do I need for safe piston to valve clearance?
 
.035 - .050" is what I shoot for.
You might give up a tiny bit of compression by valve pocketing the piston, but the alternative isn't so pretty.
Keep in mind valve float (thrown chain, etc) and rod/piston stretch.
Err to the side of too deep of pockets rather than too shallow.
A little Play-Do or modeling clay and two small pieces of Saran Wrap will help do the job. There is no one-size-fits-all dimension, as deck height, gasket thickness, and valve seat height all affect how deep (or if) you will need to machine your piston.
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🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
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32 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Good post Brian .... I agree and consider the exhaust valve to piston clearance the most important one if you do have valve float. On the exhaust stroke the piston is catching up to the exhaust valve and if it’s lagging behind because of valve float it could hit piston.

Steve
 
Will a world formula cam in a stk 206 with some stiffer valve springs. Hurt low rpm excelleration? Off corner. How much valve spring pressure to prevent valve float to 7100 rpm?
 
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