Thanks, Well interestingly enough I had these heads and intake on a 416 in 2012 and it made 563 hp @ 6100-6200 rpm with a 252 @ .050 .660" hydraulic roller. I think the small exhaust port window and header tube size is the next bottle neck. This build also re-emphasizes the absolute NEED for suitably sized heads when using a 4" stroke. J.Rob
