There are so many considerations to factor into this piston to head conversation, it is almost impossible to accept anyones " rules". There are probably ten things that come into play for what is acceptable, safe, and realistic as far as this goes, you can just make any blanket statements. Then you really need to know the driver, his skill level and his experience, which can REALLY affect what your comfortable setting some of these clearances to. I refuse to get into these debates on here,or share much of any experiences, as its usually futile, but what I will say is I would NOT take what Chevy High Performance and related magazine articles as gospel.

I have run big blocks ( steel rods) at .027 P/H clearance, so seeing a small block there isnt surprising, but its not what the typical bracket racer or street car would run. Once again, those two applications are in need of totally different considerations, and its not always the race engine that you need to be worried about.