How much material can be safely removed from the 400 and 250 cylinder heads without consequence? A buddy i know recently had .050" removed from his 400 cyl head. I think it's too much. Will it live?

 

.018-.020 MAX ON PUMP GAS.

 

Your buddy's squish band will be extremely small now resulting in too much compression. He'll end up killing it or melting down if he doesnt run race gas. Polarisfreak is correct. About .020 is max for pump gas. Your buddy needs to find another head to do, or have the squish area redone to lower the compression. Squish band clearance is of the utmost importance for good power, but compression must also be maintained which requires recutting it sometimes.Bubba