Your opinion:

For a stock 330 buildup:

Cruising boat 3200-4000 RPM non heavy throttling application.

Intake manifold: Oval Port stock Merc(second hand)

Question, The boat originally had peanut ports, machinist informs me that this intake is not the same as the heads we were going to buildup(peanut ports)

Do I have him bolt on the intake to peanuts or have him put together ovals?

This is the only intake I have and the interchangable parts are the heads thanks.

If it were me I'd put a set of old closed chamber oval port heads on to bump up the compression of the flat top pistons. I have some if your looking for a set. Good Luck.

I am just now going thru a similar exersice. If your engine is a Gen V or VI ( approx 1990 to present) the best way to make HP without going nuts is to use the VORTEC heads casting # ends with 279 these heads have the large 230cc intake ports along with the advanced style vortec combustion chamber. These heads can ONLY be used with flat top pistons. You will get approx 8.75:1 compression ratio. I picked a good used set up on e-bay for under $300.00. The best intake for these or any "large oval port" heads is the Holley #300-42 it is only $160.00 and makes great torque up to about 5000 rpm. Just make sure you inspect the interior for casting flash. Holley has had some QC issues on these manifolds. As you can probably tell I have done my homework on this engine combo. The opinions expressed are the result of many hours of research not just picking parts out of a hat.
Good luck
Charlie

Are there Differences in Marine and Auto 454 heads ?
Merc wants like 1100 each !

Other than the epoxy paint on the outside the heads are the same. Be careful buying though the heads you want are the 279 casting #'s. I found a lot of people saying other #'S are the same they are not. If you are going to do a cam change to anything over .500 lift make sure you change the valve springs and retainers and make sure you pay attention to valve overlap so that you are not sucking water into the cyl.
A WONDERFUL book to buy is ' BIG BLOCK MARINE PERFORMANCE" BY Dennis Moore. It is without a doubt the best performance money I have spent to date on my boat. Amazon has them for around $12.00 buy it and read it cover to cover TWICE, you won't be sorry.
Good luck

I would think the marine heads has bronze guides and SS valves. Anyone know?

Thanks, great info, I read Moore's Book about ten times and is a great reference.

Hey Prosnd..... good info, altho the compression ratio will be closer to 9:1. The heads measure out to about a 100cc chamber (at least mine did). You have to be REALLY carefull with your timing to stay out of detonation with these heads. Bout 28 degrees total, maybe 30 with 91 octane.

Replace the rotators with eliminators and put stock 454mag or 502mag double springs and retainers and you are good to .550 lift. That should be enough for most stock motors.....

Good luck.!