One of my better builds a W2 367 made 531HP @ 6750 and 499TQ @ 4900 with a 238 @ .050" hyd roller with a dual plane and it wasn't done. Duration doesn't dictate RPM nearly as much as induction.
Ok look at it backwards then. 1.56 hp/ci would mean a 408 stroker should make 636HP right? So why don't they? A good 408/416 with non-offset rocker decent heads can hang on to 6100-6300 rpm and make 570-590hp right? That is nowhere near 636HP at the same RPM. So why is it so hard to snag 600 HP with a stroker? Ya can't turn 'em harder the curve just drops off. Ya can throw all the cam you want at 'em and the peak rpm doesn't change either. You can change intakes, carbs, headers to your heart's content and still -peak power occurs at almost the exact same rpm. Why? J.Rob