Those heads won’t make 900hp n/a without a fair amount of rework………. same with the manifold.
You’d think if that had happened, it would have been mentioned.
I got 926 hp out of 440-1 heads, but they were ported extensively, had 2.3 intake valves, and about every trick i could come up with to get there in the rest of the combo. Huge cam, .9 mm rings, wilson ported 3x, 15/1 compression, Terminater 2500 cfm theottle body and methanol, 2 1/8 tube excellent headers and a vacuum pump. 900 hp doesn't just show up easy.
