top hat valve shims

[jabingb]

Are 8mm top hats OK on our 5/16" valve stems? I'm starting to wrap up a head but I can't locate top hats for the 5/16" valve. Alfa shims (8mm stem) are readily available in the US, are they an OK substitute, ~.0025" larger?

[rgh0]

I have 5/16th inch / 7.94mm top hat shims that I got from both QED and John McCoy, so they are available. Whether a 8mm top hat with the extra 0.06mm clearance would work OK I am not sure and i dont think I would want to try it out on an expensive race engine in order to find out, which I presume you are building if using top hat shims.

Though you dont need them for race engines these days either as plenty of suitable spring packs available that use the flat standard biscuit style shims

cheers
Rohan