wrasse

Hello all! My first post!

Have a 1991 7.4 OMC King cobra pushing a 24 footer. The motor is all stock with about 120 hrs and runs great. I think it makes 330HP at the crank.

I did some reading and thinking of the following for a cost effective upgrade without pulling out the motor.

1. Vortec L29 Heads
2. Edelbrock RPM Intake
3. Holley 750 cfm marine carbs
4. Mild Edelbrock cams

Does this combo sound ok? Think I'll get 400HP with this?

KAAMA

iTrader: (1)

You can probably go either way on the heads on a 454cid engine. The rest of your parts mods sound good, but if you are only looking to achieve 400hp, then you can still retain the "peanut port" ovals you now have and have some bowl/pocket porting done to them----BUT if you want more than 400hp, then the Vortec heads will probably be the better choice. Some of this will determine the type of exhaust you are using as well. I'm not exactly sure you'd be able to acheive 400hp with the stock Merc cast iron exhaust system, but will be doing your engine a big favor by adding an aftermarket exhaust manifold system such as a Stainless Marine, GIL or something comparable---it will help you achieve your HP goals much easier.

Call "rmbuilder"/Bob Madara of Marine Kinetics (585) 654-8583 on your cam selection and talk to him about your combo. He is honest, very knowledgable and has helped many on this forum.

BY U BOY

You Will Need To Replace The Exhaust If You Want To See Those Numbers. Also That Combo Depending On Cam Should Make More Than 400hp.

Check Ebay You Can Pick Up The Glm Aluminum Manifolds Fairly Cheap.

SINCE YOU WILL HAVE THE HEADS AND INTAKE OFF WHY DON'T YOU JUST RETRO FIT TO A ROLLER.

dean51267

Dude, buy a 420 hp 454 CRATE motor, install it, and sell yours. You get a guarantee, and it will cost the same or less. 1800runsnew.com has NEW, GM CRATE MARINE, 454, Gen 6, long block motors for $52XX.

You will spend a little more on hard parts, and a lot less on mechanic time, AND you get a warranty.

As a guy who lost $40K THIS YEAR, and a years boating trying to do EXACTLY what you contemplate, I STRONGLY suggest this path......

Strip Poker 388

iTrader: (6)

I would find a 425hp MPI that has low hours.I have a buddy that just did this in a 1988 28ft Scarab he is real happy!!!

A thought....the stock Quad on my 1989 365 mag was a 850cfm.

if ya spend very much on heads I would look at some Dart Iron eagles.Or find some chevy sq ports used in good shape that someone is moving up to Aluminum heads.

KAAMA

iTrader: (1)

Just keep in mind that the GM rectangle port cylinder heads have tendancy to CRACK between the seats! I have seen this a lot over the years.