Peanut port options
 

i have a 1988 Merc McM 330 , I assume its a peanut port cyl head type motor
as one of my many winter projects i'm gonna put on an aftermarket exhaust , and was thinking about upgrading intake and carb setup , not radical , mostly for looks to be honest , any performance gains will be a bonus

any idea's on intakes ? , what happens if i bolt a rect. port intake onto small oval port heads , will it still seal? will it disrupt fuel flow horribly ? will i blow up in a sequence that would make james bond proud?

thanks in advance

The aftermarket exhaust will at least make your engine look and sound a little nicer. Stainless Marine or GIL, Eddie Marine, or comparable manifold type exhaust systems would be a good choice.

If you're going to stay with the stock cam, then an Edlebrock RPM Performer or Air-Gap intake manifold would be a good choice. Both are dual plane intakes.

Also, as long as you're replacing the stock Merc exhaust system with a better breathing aftermarket exhaust, and you want to replace the stock Merc/GM cam with an aftermarkter hydraulic roller that runs a higher RPM range, then you could go with a single/open plane intake manifold like a Dart or something comparable.

Not sure what all you're looking to do on your peanut port heads, but you can have larger valves in stalled on the heads and have them bowl/pocket ported if you want. If you don't want the larger valves, then at least have the heads bowl/pocket ported---probably good for maybe 20-30hp or so.

A Holley 750cfm carb is what I would use on a 454cid engine.

Solid advice for that motor.

I had twin 1987 330 Mercs. I did similar to what you are thinking. I installed Edlebrock Performer intake only after I epoxy coated the entire intake since I run in salt water. I added Stainless Marine exhaust, Holley 750 CFM carbs, MSD ignition, and a slightly more agressive cam. I had them dynoed at 424 hp and 509 ft/lb torque for both engines. The peanut port heads will create some good torque which is really what a boat needs. I wouldn't install rectangular port intake as it will disrupt air flow and create a vortex. I had good luck with the peanut port heads personally. Tommy

Thanks for the advice , i really dont want to tear down the motor too far , so the cam will remain the same.
now starts the search for a BBC intake for peanut port , i see all kinds of rectangular and oval.
and exhaust , but i recently read that the stock 496 exhaust bolts up to 454 , an inexpensive upgrade if i can find someone who upgraded there 496

I have a 454 I call the Mystery Motor. It was supposed to be a Gen V 454 Mag but it's not. It was replaced at some point by a previous owner with a Gen V 454 block with peanut port heads that was built by an independent shop so I have no idea what is in the bottom end, what cam or if anything was done to the heads. It came with a 750 Weber on a cast iron Quadrjet manifold and cast iron exhaust. It has always run very strong so I'm guessing it was not built as a stock 7.4 330 but ????? Anyway, this past spring I had a set of Dana exhaust and a performer intake installed with a 1" spacer under the carb. My mechanic has a big prop shaft dyno that is not calibrated in HP but allows him to load the engine for tuning. He was surprised at how many jet sizes he had to go to get the plugs looking right. I went from a 23 to a 25" Mirage Plus, picked up 6 MPH on top end (4800RPM on factory tach) and improved my cruising economy at 3000 RPM. Not knowing what I have on the bottom I'm not going to try spinning this thing any faster than that. Speed is great but reliability is even greater in my book. The Danas are Awesome. They scavenge almost as good as a tubular header without all the problems. I highly recommend them. If you go this route, make sure you change jetting or you will be way too lean at WOT.

The 496 manifolds do fit and this is the exact route I was taking with my gen VI 454 untill my mild mods turned into a new build.... Funny how that happens.:cool:
Since I jumped my displacement up to 540 these are no longer the best route for me. If you are interested in them let me know, I PM'd you a price. They are in great shape and are the aluminum ones. Some of them, including the most recent ones, are cast iron. The aluminum ones are much lighter.

Just curious if you had your "peanut port" heads modified in any way such as larger valves in stalled w bowl/pocket port work? Or did you did you just stay with the stock valve size and still have a bowl/pocket port job done? Thanks

Peanut port heads flow around 200 CFM stock. With work valves slightly bigger (cut down some larger valves) Got the flow up to 240 / 250 about were large oval ports are stock. Ported large ovals get up in the 300 CFM range possibly more if I played around with them some 300 was using 2.19 valves. Dont recomend bigger valves on a 454 because the chambere is aprox 4.48" across which is bigger than the bore. I think with some tweeking a set of big ovals with stock size valves could see 270 CFM or a bit better which would be perfect for a 454 maxing out HP at 5200 RPM torq around 4000 RPM.

Thanks for your input on the larger ovals. It is very interesting, but would still be interested in knowing what pocket/bowl porting and short side radius work would do to a set of "peanut port" heads with and/or without larger valves? Do you have any further knowledge on bowl/pcoket port work on the "peanut port" heads without major porting? Thanks

Did not change the valve size. Did go to an upgrade material though - inconel or titanium I think. My 330's were 4 bolt mains and were strong motors. I have 2 - 525efi's in my current boat and lost both of them at 112 hours. I miss the old iron and I could work on those motors. Cam sensors, injectors, multiple coils, ... - it all sucks now a days! Tommy

full port 240 to 250 bowl port around 225 increase in valve size wasnt worth the money.

Thanks for your response Tommy. I think it is pretty impressive that you made 424hp and 509 ft/lbs of torque on the dyno without using larger valves. It would still be interesting to know if you still had the peanut port heads bowl/pocket ported with the stock valve size with the dyno figures you obtained? Thanks again

Turbo, thanks for your valueble input. Much appreciated!

I had stock heads. The engine shop did some mild porting of the heads only to match the intake. I don't think there was any bowl porting of valves. Both engines dynoed very close to same numbers. The reputable machine shop was impressed with these numbers also based on the peanut port heads. Everything that was done worked well together without any 1 items overpowering the other. I did have better performance with the slightly less air flowing Edlebrock RPM manifold in lieu of the RPM Performer though. I ran the Performer after the salt ate the non-coated RPM intake thinking it would be an upgrade.

Get some 702 style old 60's Closed chamber large oval heads, change cam, and rejet carb. Also add hi octane gas. This will wake up the motor.

If you don't want to change cams, Just put some 1.8 roller rockers on it and it is like a bigger cam. The rockers also give it a faster ramp on the cam so it works closer to a hyd. roller cam only alot less work!! You will have to put in new studs, and aftermarket valve covers, But it is well worth it . I changed just rockers on twins and gained 300 rpms a motor.

Thats a great idea , easy upgrades , thanks