I almost hate to chime-in because the thread is evolving the way I hoped it would. Thanks for everyones input. I am curious to know if any of the applications that require pressures beyond 380 lbs. over the nose are using steel retainers and or mufflers (backpressure). What dia. pushrods and wall thickness in those applications? Are the applications exceeding 380 lbs. (nose) with success using synthetic oil after the break-in period? I am beginning to think the best recommendation to give someone whos combination of parts see significant gains above 6500 rpm (e.g.-1's heads on a 446") is to use a roller cam. (In retrospect isn't that the consensus already.)