Mr. Moore,

I have a 502 King Cobra, Gen V in a 1993 Four Winns 221 Liberator. The only modifications are Gil exhaust and a K&N breather. I have read your Big Block Chevy Marine Performance book cover to cover a couple times. I would like to change the intake manifold. Should I go with the Holley 300-42 or with one of the newer Edelbrock Performer RPM manifolds? If the Performer is the answer do they make an oval port model that will work with rectangular port heads to follow the theory in your book or should I go with the rectangular port version.

THank You

The Holley is the only oval port dual plane intake manifold I have ever found that will cover the rectangle intake ports. I know that the Edelbrock doesn't. If you have the GM rectangle port dual plane intake manifold on there now it will be hard to notice a performance difference by installing the Holley (on the 502). The oval port Holley works better on a 454 with rectangle port heads. The stock, rectangle port, GM manifold works well on a 502. If you need more horsepower, install a larger carburetor but don't install a spacer.
Thanks for buying the book.
Sincerely
Dennis Moore

Mr. Moore,

This 502KC came with a Holley 850 CFM 4150 dual feed with 88 primary and 84 secondary main jets. Would going to the rectangular port Edelbrock Performer RPM give me any performance gains over the GM aluminum rectangular port?

Thank You

Just make sure you're not using a square bore carb on a GM spread bore intake.......

502 KC II
It would be hard to find a difference between the manifolds running the engine on a dyno. It would be impossible to tell the difference on a boat. The Edlebrock is probably a better manifold but not by much!
Don't waste your money.
Dennis Moore
www.mooreperformance.org