Rave Valve Clearance on a 951 DI?

[JohnCiccarelli]

This seems too simple, but I have to ask. I am about ready to have my cylinders bored and rave valves shaved, I am confused. There was a warning label that came with the piston that stated that If the pistons are .020 of more over stock that the rave valves need to be shaved .015. Mine are .020 over. I do not know why you would shave them more then the change in clearance which would be .010. What am I missing?

John

 

[Chester]

You are right. As a matter of fact, the valves come from the factory with enough clearance for the first oversize pistons (.25mm or .010"). From this point, when you go to .020" oversize pistons, you are increasing the bore size by another .010". Therefore, in reality, you only need to shave .005" off the valves to equal the clearance you get with the first oversize pistons.:cheers:
Great question!

Chester

 

[JohnCiccarelli]

Thanks, I guess I will have them shaved .010. This makes the most sense to me.