Even I get confused since I did a lot of testing. I had two 470 inch engines that I was using and I was constantly swapping parts. We ran about 150 dyno pulls over a two year period so it can be tough to keep it all straight. I think the very best runs for the 240 heads were on the 470 dry sump engine with the ported Wilson intake and a Dominator carb. Those very best runs got into the 750 range but I'm not sure I ever published any of that information. The 270 heads picked up another 30+ hp on that same short block.
My short summary is that the average guy should be able to build a 600 hp engine with the 240 heads. Pump gas 470 or 505 with a modest sized cam and a good single plane intake should be 600+ without any special parts or work. The heads can be pushed past 700 hp if you work with a good engine builder. You'll need to port the intake and pick an aggressive cam and dial in the carb and stuff like that. This is all with out of the box porting. I never touched the heads other than verify guide clearance. We did change springs depending on the cam and rocker arms but that was it. They are great heads, best ones on the market for the average guy to use.
