Help, quick Intake manifold question... which one?

[Lenny]

Tomorrow, (Friday, June 27) I need to get a new intake manifold on my 350 Mag EFI motor that is now a 650 Barry Grant carb motor.

Which one to buy. Rpm, Performer, or Air Gap?

I think the Air gap is higher than a non so hatch clearance could become an issue. This is a stock, LOW hour 300 HP 350, (Mercruiser) 1997. It has Mallory on it now and Stainless Marine.

Which one do I buy tomorrow AM. ? I drive mostly in the 3500-4000 rpm range. My stints at 5200 are less than 20-30 seconds. (weather depending)

[VetteLT193]

Tomorrow, (Friday, June 27) I need to get a new intake manifold on my 350 Mag EFI motor that is now a 650 Barry Grant carb motor.
Which one to buy. Rpm, Performer, or Air Gap?
I think the Air gap is higher than a non so hatch clearance could become an issue. This is a stock, LOW hour 300 HP 350, (Mercruiser) 1997. It has Mallory on it now and Stainless Marine.
Which one do I buy tomorrow AM. ? I drive mostly in the 3500-4000 rpm range. My stints at 5200 are less than 20-30 seconds. (weather depending)


I am pretty sure the air gap is for higher RPM stuff, so I would rule that out, but I don't know much about it in detail so take my advice FWIW.

The performer tends to die after 5200. The performer RPM is good for 6k with less low end torque.

So... Performer is my advice. It's the intake I want for my 350 / BG combo.

But.... What I can't figure out is if they make it in a marine version. Everyone seems to use them but I don't see a marine spec. on them

[MOP]

Rootsy had the air gap on his, I would get his input. I went with the Performer and a 750H and very happy with it.

[BlownCrewCab]

I Had a TorkerII on my 408, It's a single plane that performs very well. and you can still get them new for $100. If I built another motor thats what I'd put on it.

[BigGrizzly]

In your particular situation and application it really doesn't matter. You won't see any HP gain. Garry has already done the Dyno pulls. The air gap is to keep the heat away from the air charge. It is not specifically a high RPM manifold. It really performs almost exactly like the performer. So make your choice.

[VetteLT193]

In your particular situation and application it really doesn't matter. You won't see any HP gain. Garry has already done the Dyno pulls. The air gap is to keep the heat away from the air charge. It is not specifically a high RPM manifold. It really performs almost exactly like the performer. So make your choice.

Thanks for the info grizz. I thought it was high RPM for some reason.

Are any of these marine ready (raw water cooled)?

[Forrest]

. . . Are any of these marine ready (raw water cooled)?
Yea, let me know if you find a SBC aluminum intake with bronze water passages as well. The only small block manifold that I know of that has a bronze water passage is one made by Holley for their marine fuel injection system.

BTW, if you need hatch clearence, the Wieand Stealth small-block Chevrolet manifold is a little lower than most and performs quite well. I'm running Stealths on my 383 engines.

[zimm17]

None of those edelbrocks are lined for raw water cooling.

I had an RPM airgap. The airgap actually makes a difference in temperature. I could touch the part under the carb after running and it was cool enough to touch. It also acts as a small part catcher for every bolt or nut you drop- make sure you have a small magnet parts fetcher.

[Barry Eller]

Yea, let me know if you find a SBC aluminum intake with bronze water passages as well. The only small block manifold that I know of that has a bronze water passage is one made by Holley for their marine fuel injection system.
BTW, if you need hatch clearence, the Wieand Stealth small-block Chevrolet manifold is a little lower than most and performs quite well. I'm running Stealths on my 383 engines.

I'm running the Wieand Stealth on my 502. Dual plane gives better midrange throttle response, so I've been told.

I purchased mine from Eddie Marine. They will anodize them for salt water use.

[MOP]

I would not worry about finding a manifold with a bronze lining, Merc and some others have tried it and it does not last as long a raw aluminum. Salt guys check your local shops, they are going to say 5 years before they burn through and soak the engine. I and many others have seen some decent life out of plain aluminum, even in the case of exhaust actually better then iron. It is no different then your 95% all aluminum out drive. Bob (Tilbet) just went through it!

[MOP]

I remember Rootsy saying that with the air gap the engine was cranky when cold, if you spend some time researching dual plane gives smoother performance. Another point is on raw cooled it will take extra time to get air gaps up to temp where it will run decent with a 140 Tstat, on closed cooling they should act just like they would on a car due to the quicker and higher operational temperature.

[Rootsy]

FWIW,

I prefer a hotter running engine... hence I run a 160 thermostat with raw water cooling...

My old engine was never really cold blooded... fired right up without any issues... I always give it one or two pumps before cranking and when you hit the key she'd fire right off.. I never let em idle cold anyway... I put it at high idle to get some temperature built up without hogging a dock for 20 minutes...

Don't see any reason my new power plant won't perform the same way if not better.

I like the RPM airgap... especially for engines with some breathing capability...

[BigGrizzly]

I too like warmer engines. I always run closed cooling. even my blower motor has a T-stat. Everybody told that that was wrong, and I could not closed cool that motor. Suck my wake. Now lots are doing it with out an issue. Just imagine what I could do if I knew what I was doing!

[yeller]

I would not worry about finding a manifold with a bronze lining.....I agree MOP. I don't know where or how aluminum got such a bad rap. IMO, aluminum will outlast iron intakes/exhaust by years...salt or fresh water.

[BigGrizzly]

I just checked and the bronze manifolds do worl providing there is no other aluminum pieces in the system and you always use a disconnect switch, when not running, to the batteries, that disconnects the GROUND and the positive. Every one we have seen bad had some installation problem or left the power on when in the water. I am going to get blasted by you non closed cooling system guys, but a closed cooling is cheaper then waiting to have a problem. I don't know anybody with a pleasure boat that takes off the intake just to see if it is corroded.