My 10/1 compression 408 made 504 hp with a dual plane intake and a hydraulic roller. Add compression , Race roller cam and a tunnelram, plus other power adding tricks, and that says there is a lot more hp available IMHO than 550. A good rule of thumb is, if you have a well designed head, 2.4 hp per cfm you are using is reachable. My 528 wedge has pushed a 3065 lb car to 8.70s at 153 in 1600 da air, with a net .730 lift cam, which reachs about 370 cfm of flow on the heads. You need at least 885 hp according to dragtimes calculater, ON THAT DAY , not dyno hp. That works out to almost 2.4 hp per cfm. So IMHO a head that will flow 280 cfm, which i think they can reach fully ported(?) considering my bowl ported EQs went 272 at .600 , ought to be able to go 625 plus or more, which is only 2.2 hp per cfm.
