Once upon a time we ran a 7.85:1 compression 440 on the dyno with a 108 LSA 509 cam. 850 cfm Mighty Demon, 2" Super Sucker spacer, M1 single plane, 516 factory iron heads flowing 250 cfm @ .500" lift and our dyno headers. 460 TQ @ 4,200 rpm and 449 HP @ 5,300 rpm. The 600 HP 452 heads were flowing in the 300 cfm range @ .600"