35thls1ss19

So my head gasket went and took a chunk of head with it. Between cyl 3 & 5. So my question is what are my options? Go with large oval port heads? Then will i need a cam?

Or just throw stock heads back on? Change intake and rockers?

What do you think my best bet is for makin more power or shoudl i get it running get the rest of the season out of it and rebuild over winter? thanks guys

picklenjim

330 should already have the large oval port heads on it. I would just find a head to replace it and get it running at this time.

wjb21ndtown

I wouldn't throw those garbage peanut port heads back on that motor.

Does your boat have twins or is it a single?

If it is a single I would buy a set of large oval GM heads, casting #'s 781 or 049 preferably (in order), throw them on and be done with it. You'll get decent gains, the heads will cost you the same as a set of peanut ports, the motor will breathe better, and you should pick up some RPM.

If its twins it gets a little more problematic. The GM heads have different CCs in their combustion chambers over the years, even for the same castings. It may be difficult finding a set of four that match, but IMO it would be worth it.

picklenjim

Another thing I noticed on your other thread that you have a Alpha drive. Mercury only made the big block for 2 years with that drive. There was a reason. They can't handle them. I would advise you keep that motor completely stock. You are already over the limits of that drive.

Also you said those were new heads you put on last year. If you burned a spot between 2 cylinders then you have some other problem you need to figure out.

Too Stroked

I'll second that opinion.

socalstone

The 330 hp 454 used the small oval port (peanut) heads.
I wouldn't touch them again. I changed mine to rectangular port and absolutely love it. Really lets the motor breath. I did the ho cam and ho intake at the same time which of course helps. If you don't want any more performance than use the same 330 heads as was on there. But if you want an easy upgrade - do the rect port.

35thls1ss19

i would def liek more performance and i am not to worried about the drive, i will just put a bravo on if i blow it. I have some access to one along with a transom assembly

PatriYacht

Edelbrock oval port heads are a great replacement if you are boating in fresh water. They are aluminum, fairly cheap.

BY U BOY

I second that.. I did the GMPP ZZ502 Heads on mine and really woke the engine up. Also did the zz502 cam,intake BG 830 Carb 1.7 Rockers and 10:1 pistons. PIcked up 10MPH in my 21 Scarab.

Good luck

dba900

How much power can you make with these? I was under the impression that the cast internals couldn't handle much power.