Stocker P/v clearance

[Alan Roehrich]

Originally Posted by Robert Simpson

What p/v clearance in the min you run in a sbc automatic stocker? Also what valve spring pressures do you recommend on the seat and open? Thanks for the help

You need to talk to your cam grinder about valve spring pressure, there's no way to tell you what you need without knowing the lobe profiles. The aggressive lobes will often want 200# on the seat, and maybe a 500# per inch spring rate.With those pressures, you're going to need 7/16" rocker studs, minimum, and 3/8" x 0.125" wall pushrods. That assumes you have light valvetrain components, such as hollow stem valves and light weight tool steel retainers.



For piston to valve clearance, on the intake side, you can run your total deck clearance, plus 0.010" for a safety margin.On the exhaust side, you'll want 0.065" or more. You want to check that with your as raced valvetrain, and a dial indicator on the retainer.


Also, those numbers assume you have good engine RPM control. And that doesn't mean using a rev limiter to control RPM on the burnout. Ask Pro Stock legend David Reher what he thinks about valvetrain behavior on the rev limiter.