schurgervt

What is the best low cost option for improving power from a stock, worn out 330 hp 454 with a bravo drive? I could rebuild and port it but how much could i exspect from those peanut heads? I also have a Holly Projection which might be more economical than the Quadrajet. I think if I could buy a take out later model injected engine but that still could get exspensive. Any sugestions?

5050

If you rebuild I would definately get rid of the peanut heads. I wouldn't put any money into those heads. What kind of power are you wanting to make?

ThruHull

I have a complete take 7.4L MPI with low hours cheap! pm me if interested.

KAAMA

Have you done any searches here on OSO in ref to upgrading the Merc 330? Try searching for "Merc 330 on steroids". Just know that the Merc 330hp/454cid engine has cast cranks and pistons. I am sure there are a lot of guys on here who can tell you about their experiences with the Merc 330's they have upgraded.

Is it a dual engine boat? What kind of exhaust system are you planning on using? If you're only going to stay with the stock Merc exhaust it should have an effect on how you should cam the engine. Are you interested in upgrading to a roller cam and lifters or not? What kind of HP are you looking for?

There are several ways and options you can go with when upgrading a 330. Not sure how much HP you're looking for, but If you really want to keep it simple and low cost, then I would stick with a Holley carb induction vs a EFI version. If you stick with the stock rods, cranks, and go with forged pistons, use the same "peanut port" heads, retain the same stock valve size (2.06" Intake valves/1.72" exhaust valves) and just have the heads bowl/pocket ported by a competent head porter and buy stainless steel valves. Add an Edledbrock Air-Gap intake manifold and add a upgraded cam (depending on exhaust system) and you should see well over 400hp.....MORE with a better breathing aftermarket exhaust system.

BY U BOY

I upgraded mine last summer to
ZZ502 aluminum heads
ZZ502 cam
Roller lifetr/rockers
ZZ502 cam
ZZ502 intake
DEI Ignition
Srp 10:1 pistons
Barry Grant 830cfm DP
Marine power Exhaust
Stainless cross over
Holley 130GPH fuel pump and regulator

I never dynoed it but estimated power is between 500 and 530
I picked up 11mph on a 21 Scarab with a little more tweeking to do with carb and props.

Good luck there is a ton of info on this subject.

KAAMA

My cousin has a 1988 32' Baja with a pair of stock Merc 330's that he upgraded on a low budget. He reused the stock GM cast cranks (turned 10/10), reused the stock 3/8" rods (shot peened, reconditioned, and added ARP rod bolts), new cast pistons (told him to go with forged pistons, but he didn't), replaced the stock cams with some higher HP cams (flat tappet hydraulic cams), roller rocker arms, dual plane hi-rise intakes, stock Merc Thunder bolt ignition, Holley carbs, some old junk GM semi open chamber oval port truck heads that he upgraded to all stainless 2.19" intake valves and 1.85" exhaust valves and had the heads bowl/pocket ported by "jimV". The blocks were 2-bolt mains, and he had them "Bore notched" for more power/torque (20-30hp), and upgraded to some GIL exhaust manifolds and dry pipes.

On Tom Earhart's dyno (dyno headers) he made 461hp @5100rpm and 510ft lbs or torque @5000rpm...not too bad for an 8.6 comp ratio engine! He gained at least 10mph in the midrange cruising speed and his boat runs somewhere between 69-70mph GPS.

KAAMA

How much were the ZZ502 aluminum heads and where did you buy them? Thanks

Chris Sunkin

A complete Mercruiser 330 has way more value than a used 4-bolt block and a steel crank. If those are the only parts you are retaining, sell the 330 and pick up some nice used heavy-duty parts that will make your setup live longer.

Exhaust is going to make or break whatever you do. The merc manifolds aren't going to let your 500 hp 454 put out 500 horsed. They are likely to cost you 100 of them. Remember that a high-performange marine engine needs at a minimum a sever-duty stainless exhaust valve or preferrably Inconel. You also need a couple thousandths more piston clearance and about one more on the valve stems. Marine head gaskets too- Fel Pro, Cometic or the solid copper. Copper freeze plugs too.

BY U BOY

I did some horse trading the owner of marine power for them.

I'm pretty sure that edelbrock makes them.

Knot 4 Me

Baker Engineering setup a buddy of mine's '96 7.4L's with Brodix aluminum heads, roller cam/lifters, Dart single-plane intakes, Holley 4150's, and CMI E-Tops. Dyno'd at 465 HP on 89 octane gas. Keeps revs to 5,000 max. So far, the bottom ends are holding up fine but he knows it is a matter of time before he needs to put this top end setup on a pair of 502 short-blocks.