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Old 03-05-2013, 01:26 AM
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The absolute minimum needed on the intake valve is .060" net with lash accounted for. (set the running valve lash)
This assumes that you will be using a valve spring that will not allow the valve to float or bounce at high rpm.

You can move the cam a bit to get more intake VTP clearance.

The depth does not tell you about the valve radius clearacne in the piston notch.
If the radius clearance is also tight the valve may kiss the edge of the piston knotch.
Its not that big a deal to take it apart and make the valve relief a little deeper and or make the radius a
bit bigger. (you will only need to do it once as compared to the big mess if the valves do kiss the piston at rpm)
This is a common common issue on most all BBC pistons. ESpecially the factory crate motor pistons. like the 502-502HP motor.

you need more clearance on the exhaust side as the piston chases the exhaust valve.

Whenusing a KB piston with a oval port head or any non factory head you must also verify piston dome to chamber wall edge clearance @ TDC. Sometimes minor chamber wall edge clearance grinding is needed too.
You need to check this and the valve relief radius clearance around the open valve too.

you cannot do any of this using a hyd lifter.

Last edited by F-BIRD'88; 03-05-2013 at 01:31 AM.
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