I'm going to be intalling a First Intake Manifold on my 355 sbc motor. It can be ported pretty big. I believe it comes from the factory with a 1.75" diameter or a 2.4" CSA.

Just wondering if anyone has experince with what a good CSA would be? The max rpm should be around 6300 rpm or when the power drops of dramatically. Total runner length including the heads will be 12-13 inches. Looking for peak torque to be around 4800 rpm.

 

tell us more about your motor. what heads? what CSA are the intake ports?

 

The heads are Dart Pro One 200cc aluminum heads with 2.05 intake valves. Not sure of the minimum CSA of the heads but the opening has been ported to a Felpro 1205 gasket. With the First intake manifold I can go anywhere from a 2.4" CSA as cast up to a 2.9" CSA.

 

Not enough info. Need valve sizes, minimum intake port CSA, ~VE, and so on. An unscientific way to do it is to start by port matching with the heads and then to flow it. If it flows the same as the heads, stop there. If not, open it up some more. And so on.

Rich

 

Thanks Rich. Thats what I will do. My heads flow 264CFM at .500 and 276CFM at .600. So I will open it up until it matches the heads if not slightly more. I will use the same guy that flowed my heads as it will be on the same machine. Been gone for a few vacation days.