[PJ10]

Thanks for your input. As a couple of you have pointed out, the laws of physics would imply that the tapets are loose when cold and tighten up (less clearance) when at operating temperature. I believe this is why some put in hydraulic lifters instead of using solid. They take up the cold 'slack'. Bad thing with hydraulics though, they will float long before solids! There is quite a valve 'slap' when cold with solids in an aluminum block. HP is being lost and wear is introduced over time.

I read that this is why HM (Holman Moody) prefers cast blocks. Their cast blocks (FORD Blueprinted) should be in production in the fall.