Hi Fellas,

1990 Switzer 240ss. 454 / 365 - B1 1.36:1 - Prop:
21p Yamaha Saltwater Series. 62mph @ 4500.

I have a set of cmi fusion headers, and edelbrock 6155 heads. Will these two additions gain 4-500rpm and let it spin a 23p Mirage in the 46-4800 range? Thanks for any opinions. Appreciated.

Stan Weiss' - Cylinder Head Flow Data at 28 Inches of Water -- DFW / FLW Flow Files for use with Engine Simulation Software

I can’t find flow numbers here. If someone knows the equivalent non marine PN that would help.

If the valve size and chamber size are the same, I’d say you probably won’t gain anything over the stock rectangle ports.

If you have a big valve put in, then shave them down to bump the compression ratio, now you’d be getting somewhere.

I can’t tell what CMI fusion is. Can you post a pic? If it’s full length it would definitely help, if it’s a shorty, it will help a little. Full length headers pick up even more with a cam that has overlap. Upgrading the cam to a 741 would really wake it up.