Buying the right size heads

[BrianB]

Is there a formula used to determine the correct size head for a particular engine size and rpm?
I bought a set of CFE 350cc heads to go on my 548 Chevy and I'm worried that they may be too big.
The engine is for a jet boat, so I need to concentrate on building power from about 5500 to 6200 rpm. The old 540 engine pulled about 5700 rpm on the engine and 6700 rpm on a 325 shot.
An engine builder that I have been dealing with says that they will be fine since I don't need to worry about lower rpm power. But I'm worried how much power it will have N/A.
Brian

[Mike Stark]

I'd say your right in the ball park. The CFE stuff works real well.

[BrianB]

Can you use a ratio of port volume to engine size to compare velocity in different engine combinations?
Something like:
a 540ci with a 350cc head is a 1.543:1 ratio - therefore since a 454ci with a 294cc head has the same ratio, it should flow with the same velocity.
Brian

[Mike Stark]

It's not black and white like that. Total volume will not tell you the whole story. While the same type of heads can be compared with volume, the cross section must still be considered. You can use that formula for some basic comparisons, but the smaller engines are often more efficient and can sometimes still use the larger heads.