OK, I've been thinking about all that was posted in the previous thread regarding the 572 and "choking it". In choosing a proper head, I'm of the mind that you need enough port flow for 110% VE at peak RPM. In reality, I think it's more like 110% VE at the torque peak, but I'm on thin ice here. Obviously I must be wrong on some point since everything you read points to using much more air flow than just 100% cylinder filling.
The reason for my question is 2 fold, general curiosity and also I'm at the point I need to buy some heads for my new build. The application is a flatbottom drag boat destined for the 8.0 bracket class.
My new combo is a 588 BBC (4.5 Stroke 4.560 Bore), will end up around 14.5 CR with the pistons I'm using. With that much stroke, I don't want to rev it much past 7800 or so (to high piston speed) I'm guessing my cam will end up around 280 [email protected] to make power around my target RPM. In the past I've had good luck with 110 degree lobe centers in slightly smaller combo. Finally, I'd like to get close to 1000 HP.
Based on 100% VE at 7800 RPM, it calculates to 331 CMF. That's theory, so what's reality? Based on budget and existing components, I seem have it narrowed it down Dart Pro 1's or Brodix -2Xtra's with the Darts slightly ahead. The Dart 345's advertised flow is 397 intake, 266 ex @.800" lift using a 2.300 valve. Not bad, but the exhaust flow seems a bit low compared to intake. The 355 CNC's bump that up to 415/303 CFM.
So is it really worth the extra $$ for the CNC ported heads? Engine Jr. thinks so. Each 20 CFM seems to be worth about 60 HP. However, it's a fairly basic program and not sure how accurate it is at these HP levels. It did pretty good with my SBC stuff, but who knows.
So guys, help me out and let me know what you think. I know I asked a lot of questions, but any feedback will help. Thanks!!