carter38

Fixing to freshen up a friend of mines 454 330hp. He is wanting to step it up a bit maybe around the 450hp range. What do you guys suggest. Bore, heads, cam, intake and such. It is going in a 242 Baja.

Thanks in advance.

deboatmon

I suggest swapping for a good, almost new 502EFI from somewhere. The added torque is worth everything and you don't have to have a radical cam or idle. Torque is where it's at.

carter38

That what I would like to see happen but just trying to keep cost to a minimum.

Pat McPherson

All of the above...
Lots of threads on this subject.

BY U BOY

THIS WAS IN POWERBOAT MAG JAN ISSUE

PROVEN 7.4 CARB UPGRADE
QUESTION: A few years ago you listed an intake, cam and head combination for upgrading a stock MerCruiser 454, 330-horsepower engine (mine is a 1987 model) that was good for up to 425 to 450 horsepower, if I remember correctly. Could I get that parts list? I looked through the archives, but have had no luck finding the article there.

Brad Anderson
Scottsdale, Ariz.

ANSWER: The article was in late 1998 or early 1999. By coincidence, one of the project boats that you are referring to was just in my shop for service and is still running strong with about 350 hours on it since the upgrade. There were actually a couple of stages to the upgrade. The simple one involved changing the heads, intake manifold, carburetor, ignition and the exhaust. The other expanded internally by installing a hydraulic roller cam setup, pistons and Manley H-beam rods. A few of the part numbers that were used at that time have changed. In order to make it easier for you, I have researched the parts and can provide their equivalent numbers.

The first stage of the upgrade included Edelbrock marine head assemblies (Part No. 61459), Dart oval port intake manifold (Part No. 6204), Holley 830 CFM carburetor, IMCO PowerFlow exhaust system, MSD complete marine ignition system, Manley push rods (Part Nos. 25795 and 25796), Crane rocker arms (Part No. 13750), and an upgraded flame arrestor and necessary accessory parts. The version of the Holley carburetor that was used is no longer available so I would recommend the Holley 9022 marine carburetor instead.

The second stage of the upgrade used all of the above parts plus some internal parts. The pistons were changed to a JE forged piston (Part No. 106904), the rods were upgraded to Manley H-beams (Part No. 14060), the cam was upgraded to a Crane hydraulic roller (Part No. 139731), the lifters were upgraded to Crane (Part No. 13532), the required push rods for the hydraulic roller setup are Manley (Part Nos. 25818 and 25855), the timing chain used is the Crane billet roller (Part No. 13977), and the oil pump was changed to a Mellings high-volume (Part No. HV-77). Obviously, there are many other small parts and gaskets required to do the job, but these are the main parts used with proven success.

jryan26

B & M 250

Pat McPherson

I have an extra set of Chevy L-29 large oval port heads if anyone is interested.
They are a nice cheap upgrade from the stock round (peanut) port heads on the 330s. With flat top pistons the CR is about 9:1 and they do flow better than the round port heads.
$300 plus shipping.

BY U BOY

NEW OR USED I ALSO AM CHANGING MY 454 ON MY SCARAB 21 TO GET A LITTLE MORE POWER

Pat McPherson

Used.
Approximately 200hours on a 1999 7.4.

powerquest 380

look at crockett marine. they have an upgrade for that motor, adds about 110hp. Im doing it to my 502s later this year.