Friend is putting together a 347 and he will be using AFR 185's, Edelbrock RPM II intake, custom cam, 1 3/4 full length headers, 75mm t/b and 80mm MAF sensor. After a tune, what kind of horsepower should he have at the rear wheels?
Should be around 400 easy depending on the cam. But know that RPM II is more for the upper rpm than the standard RPM, even though it's supposed to have the same RPM band. It'll pull all the way to 6800-7000, I've seen one do it.
There is a very basic reason larger cube engines need more duration - it is the ratio of displacement growth to limited valve size growth. Since the valve size is limited much more than displacement growth, more duration is needed to fill a cylinder.
Yep, 302 cams don't need all that duration because it wouldn't do any good, the cylinders can only feel up so much...larger displacment has more room to fill. So let the valve be open longer (longer duration, ex: 228...to 238*) to allow more air in.