BUIZILLA

my 330 was a 1980 vintage.. went 66.xx with only a mild cam change and mild porting, stock center riser exhaust and Qjet, went to a 454-425 HO crater, tried 5 different carbs and SSM manifolds, and it still stuck at 66.xx... both turned 4950, same prop, you tell me the 330's potential..

Crazyhorse

I'd say the 330 was running pretty good when you pulled it out.
Oh yeah, for all you west MI guys lurking out there, I'm putting the superchargers back on for next season.

KAAMA

iTrader: (1)

My 32' A/T had some 454's that were bored to 468" with some ported Merlin oval port cast iron heads and 2.30" intake valves, Dart single plane intakes, 850cfm Holley carbs, Crower mechanical/solid roller cams, 9.5 cr, 36* timing that dyno'd around 600hp @5500-5700rpm with car dyno headers, no accessories and the torque was right around 590lbs @4800 or so. Not too shaby for oval port heads---it pushed my A/T at about 83-86mph or so with Merc TRS dirves and 3-bladed Mirage Plus props. (My A/T has Bravo One drives now, but was originally built with TRS drives.)

With the heads that GM only had available at the time, Merc didn't have much of a choice when it came to heads back in the 1980's when they had their 370hp, 400hp, 420hp, 425hp, 440hp, etc, 454 engines. And as was mentioned, the oval port heads that were available from GM only had the 2.06" intake valves with the 1.72" exhaust valves compared to the 2.19" intakes and 1.88" exhausts on their rectangle port head.

I mean, I don't know....seems to me that an oval port head (ONLY if they had larger valves and some bowl porting) like some Merlins would work better on a 454cid marine engine up to around 5500rpm. If they were my 454's I would not put a GM rectangle port head on them....but hey, what do I know??? I just kill bugs for a living! I am sure someone knows more about this oval port vs rectangle port head stuff on a 454cid engine for a marine hi-perf application up to 5500rpm, but in the mean time this has been a fun thread with all the input---even from my friend Crazy Dave the horse!

BUIZILLA

that's a very good combo of parts...

Crazyhorse

Yeah, he ain't got JC Whitney stuff in these motors either.
Good talking with you this afternoon, KAAMA. I hope we get to run together up north next summer. Mac Island, Hessel, De Tour.

It ain't the pot that gets you high, it's the papers. Always double-roll.

cuda

I'm curious to see what the exhaust swap does to this 1982 454/330. If nothing else, I weighed the old log style and the new Dana, and saved exactly 90 pounds. Once I run it with just the exhaust change to get a baseline, I'm going to change the intake and carb, and run it again.

KAAMA

iTrader: (1)

Cuda, if your Merc 330 is of 1982 vintage, then to answer your question "yes" you probably have the larger, better "049" casting GM oval port heads on it. Which is probably one of the better flowing oval port heads GM ever produced. The problem is that if you ever install stainless valves you should install hardend seats with it as well.

cuda

I'm almost positive it is. I don't think there were ever many hours put on this engine. The more I take off of it, the more I'm amazed how good things look after 25 years.

cuda

When I change valves, they will be on another set of heads, and block.

Crazyhorse

And yet again I have to slightly disagree with my esteemed colleague KAAMA. The heads of that vintage have flame-hardened exhaust seats and wouldn't necessarily need to have new seats due to a valve change.
The truth is that the seats will probably get changed because of installing larger exhaust valves, if not also because the seats are sunk so far down you'd need a rope ladder to climb down there.
The intake side can be ground to accept the bigger valves if that is being considered.
Get the heads cut for teflon seals when the guides get replaced.