first off, considering that P/V clearance is not of much concern, what kind of preload range do our lifters have? i know that with a small BS cam and .030 off the heads will work w/ factory p-rods. i did it. but what im wondering is, how much can the heads be milled and still keep the factory p-rods? i've heard of somone on here going .040 off the heads and running factory p-rods but im a little skeptical on that one. what im thinking about is putting a .010-.030 spacer under the rocker arm rail, and going .050-.060 on the heads. anyone have any expierence here?

 

In a discussion a long long time ago with Geoff at TR, he told me he had put a stock lifter in a vice and measured the max preload. He said he had gotten it above .100, and close to .200. So in some ways, the lifter preload in a static situation may not be a problem. He did not test to see if there was lifter pump-up at higher RPMs with significant preload, though. The more preload you add, the more I would be worried about lifter pump-up at RPM and subsequent loss of power, if not major p/v issues.

chris