Did you also re-use the stock cast crank, 3/8" rods, and cast pistons while upgrading the HP to 425hp from the Merc 330 ??? Or did you swap to all forged internals? Do you happen to remember what RPM it made 425hp at?

About 5 years ago my cousin rebuilt his Merc 330's. He went to 461cid, retained the same stock cast cranks, 3/8" rods, and installed new cast pistons and 2-bolt main blocks. The only thing he did to upgrade the stock rods was had them shot peened, and replaced the stock rod bolts with ARP rod bolts and reconditioned, had the rotating assemblies completely balanced and the blocks align honed.

He used some old JUNK GM large oval port semi open chamber heads that he had JimV install 2.19" intake valves and 1.85" extaust valves and did some bowl/pocket port short side radius work on the heads. Funny, the 1.88" exhaust valves did not work/flow as well in that particular head because of the way the chamber was designed....the 1.88" valves actually were too large and did not flow as near as well as the smaller 1.85" exhaust valves...at least in this reference.

He used a hydraulic flat tappet cam of 218*/226* (at .050" lift) .515"/.515" lift on 110* lobes, dual plane intake manifold, Holley 830cfm carb, and had the cylinders in the blocks all "bore notched" to unshroud the valves for better flow, 8.6 comp ratio, 32* of timing, and they made 461hp @5100rpm and 510 lbs of torque at 3600rpm on Tom Earhart's dyno with car dyno tubular headers.

Torque stayed very flat up to 5000rpm. He could have used a cam with more duration, but we wanted to keep the RPM's at about 5000-5200rpm because of the cast pistons just to be safe.

The engines were installed in a 1988 32' Baja and I think it would be fair to assume that the engines have lost about 25HP going from the dyno headers to a dry piped GIL exhaust manifold in the boat. He has only tried one set of props (went from a 21" 3-blade to a 25" 3-blade) and said he picked up 10mph in the midrange and on top.

I believe that a lot of people get all wrapped up about 4 bolt mains, and 7/16 rods and such. 425 HP is nothing for a 454 today. If you were to use ARP fasteners, Edlebrock intake, good carb and cam, some clean up of the heads, and a seasoned engine builder that has good attention to detail, you will have no problem reaching your goal.


Darrell.

That sounds like a hell of a cam. Which one did you use?

Fastenough, Those peanut heads have a ton of material in them. You can either buy the Merlin large oval ports( around $750 each fully assembled in JEGS catalog) or you can take those peanuts to a good engine builder and have him cut a ton of material out of the intake ports.

You can make pretty good power with those stock heads.

A freind of mine who has been building BBC for a long time put those peanut heads on a flow bench in stock configuration and found that they will flow all the way to about a .550 lift cam.

I have a couple sets of the merlin ovals myself and they work really well.

Thanks everyone for you help. I talked to a Performance shop here in OH that does race cars and some boats and they told me about the same recomendations as all of you. They said some head work, intake, and cam and 430hp very easy to achieve. They said they would check they bottom end and if it needed redone total would be around 3k. That seems like a good enough deal. I think I might go this route in a few months. Thanks again for all the good advice.
Brent:D

Still wondering about that cam ghitner used?

One more question for everyone
 

Do I really need the cooler for the oil and pwr steering?? Not sure how well the old system is working anyway. I use syn oil, just wonder if the oil will really get that hot under normal running condidtions.:readinghelp:

Yes. Oil coolers are a must.



Darrell.

Yes, you need the oil cooler with the extra power. I know this sounds screwy but I have that also. The company sent me two of the one I'm using because I thought I was going to a dual engine in the future. it is a P/s and Oill cooler like stock. I also have the custom pushrods for this setup that you will need for the Merlin heads. As far as the peanut ports? My opinon is throw them away. They will never make power in the range you are looking for. NEVER. Start with the GOOD basics. This combo took my boat from 46 MPH to 63 MPH Fact on GPS.

Lunati 612/ 612 lift, 112 Deg lobe center w/ no reversion issues...duration I can find for you, great cam with excellent dock etiquette. I would run this again for a non blown application. Do you need a part #????