Thread: GT 40 P heads Biggest cam with stock rockers

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Here are just a few variables that come to mind and the reason nobody can give you a definitive answer....
Piston deck height
Piston crown configuration
Piston valve pocket placement and size
Valve size
Gasket thickness
Valve seat location relative to the deck of the head

When you first think about my explanation, you might think that you should just check it with the piston at TDC. The thing is, at different piston locations in the bore, the valve might drop down into a pocket, whereas it missed the pocket in the position before or after. That's the reason I said to check at different piston locations in the bore.

Valve to piston clearance will normally be tightest on the exhaust valve during the overlap period when the piston is chasing the exhaust valve back onto its seat.