Chip, a zero deck block with a M4F cam will have should have .060-.080 valve clearance at TDC on overlap, both valves open.060 is on the close side, ok if you don't rev the engine too high, my 261 runs .080, no problems with a compressed head gasket thickness of .038.The M4F has a small overlap, makes valve to piston clearance less of a problem than some other grinds.If your head has been milled ,you may have a problem, you or the machinist must check the clearance, don't shine it on thinking it'll be fine.Check the clearance before decking or milling,resist sinking the intake valve , it kills more power than the slight raise in compression gives ya.Not going to put a 421 SD in than Chevy, huh?
