max compression on pump gas\steel cylinder head\241 @ 50 cam

T67, Pressures in any engine are only based on three variables: Stroke length, ring/valve sealing, and the intake closing point. So any two engines could have exactly the same readings regardless of the cam/displacement. I've run big block open chambers at 185psi with no trouble. I've also had quench-built closed chamber iron heads that had 190psi that were prone to ping without careful attention to setup. It also means in terms of pressures in the cylinder in relation to the burn and piston/crank angle that different strokes require different amounts of lead to have the cylinder reach peak pressure on the piston top when the crank is around 18° past TDC. The longer the stroke, the longer the piston stays at TDC before moving away and the longer there is for pressure to build before the crank is in the best position. Some 3.31 engines running open chambers may like 40°, some 4" engines may only like 28°... Nevermind adding altitude, fuel type, and convertor/gearing into it. Back when he was new and less educated RyanJ used to used blue dye to simulate and watch liquid flowing through his port and valve job. He used to post on Moparts to more experienced guys to work things out. It was wild to see what minor adjustments in the porting or seat/back-cut angle could do for getting a poorly mixed liquid into the chamber to burn effectively. It's the liquid fuel that is the problem with open chambers, plus as 1Wild says all that dead space above the top ring and between the bore/chamber edge/gasket ring.