Upgrading to a 4bbl Carb?

Boomyal · Nov 19, 2003

I've decided that my 28 y/o Gulfstream should go out in a flurry of ping pong balls.

Call it a midlife crisis or whatever you like but after all these years of faithful service the venerable old 302 is finally gonna get a cam and carbuerator to match those under-utilized 351w heads. After pulling the interior out of the boat, in preparation for the soggy floor reconstruction, that motor was just hanging out there, in all its glory, begging to be tinkered with.

I'm currently working with Crane Cams to select the proper camshaft. They are being the most helpful and thourough of any I've talked to. The next item I need to select is a 600 cfm four barrel carbuerator and manifold. Does anyone have an opinion for the simplest, most reliable carb brand and the best manifold to use? I am running a closed system with coolant.

bluewater19 · Nov 20, 2003

Re: Upgrading to a 4bbl Carb?

I'm glad to hear that your upgrading to a HiPO marine cam. You might want to do roller rockers while your at it. They don't make horse power the just free up horsepower by causing less friction. It will really help. I would talk to holley about the marine carb and intake for your motor. Edelbrock also has a very helpful tech support e-mail. Just a thought.

Boomyal · Nov 20, 2003

Re: Upgrading to a 4bbl Carb?

Bluewater, do you think that there are roller rockers that do not require head modification? The little I've seen requires it. I just had my heads reworked and do not want to pull them off again. Since I originally posted I am zeroing in on the Holley 4160 600 cfm marine carb. It would be good to talk to Holley re a manifold. Stock or aftermarket. Dual plane vs single plane, etc etc.

LubeDude · Nov 20, 2003

Re: Upgrading to a 4bbl Carb?

Ive seen alot of holleys on boats, maybe they lend themselves to be more easily coast Guard approved! I always thought they were just concerned with the spark arrester (air filter) or lack there of! I used to be a di-hard Holley fan through the years but then started messing with the Carter or edelbrock AFB Carbs! They are much easier to tinker with! Well, maybe not easier, but much more adjustable! I like the metering rod Idea for fuel economy and they are very easy to change! You can change when the metering rods move by changing a simple spring! You just need to buy a "strip kit" you get a bunch of jets, springs and metering rods! LubeDude

SS MAYFLOAT · Nov 20, 2003

Re: Upgrading to a 4bbl Carb?

I put Holleys replacement for a quadrajet on my boat during the last season a 650cfm. It helped my boats performance and efficiency noticably. I think it could go a little bigger on the jets though. It is on a chevy 350. I think I would go with at least a 650 on yours. You can always down size your jets if it is too much for your cam, but it is there if you need it. SS

snapperbait · Nov 20, 2003

Re: Upgrading to a 4bbl Carb?

Holley 600 and an Edelbrock Performer intake manifold

.. That manifold's useable RPM range is right where you'll need it to be (off idle-5000rpm).. It is available in a powder coated marine version, or just use the plain one since you run a closed cooling system... Roller rockers are available for both the stud type mount and the bolt down pedistal or rail type mount... If you can, go with Comp Cams Pro Magnum (chromemoly steel) rockers.. They cost a little more than the el-cheap-o aluminum jobs, but they last longer and are actually lighter than the aluminum rockers...

Boomyal · Nov 21, 2003

Re: Upgrading to a 4bbl Carb?

Hmmm, the cost is starting to skyrocket. The closer you look the more possibilities come to lite, such as roller rockers, possibly a new wazoo timing chain, etc etc. This idea started out for a new cam and possibley a re-jet of the ole two bbl holley. Now it's a cam, manifold, carb, roller rockers, wazoo timing chain. Am I leaving out anything? Maybe I shoulda done this when I was 28. HAS ANY ONE HAD EXPERIENCE WITH EDELBROCK MARINE CARBS? THEY HAVE A 600 CFM MODEL, THAT IS CHEAPER THAN HOLLEY PLUS THEY CLAIM IT'S EASIER TO ADJUST AND HAS NO POWEVALVE TO BLOW OUT. Lubedude, you mention Carter and Edelbrock in the same breath?

Bondo · Nov 21, 2003

Re: Upgrading to a 4bbl Carb?

I'm Also a Believer in the "Carter" carbs.... From my own observations, the Carter, the Eldebrock, the Merc./Weber carbs are All Exactly the Same Carbs....... I'm using the Carter Street/Strip kit for tuning my Merc./Weber carb..... Needles, Jets, Springs, Needlevalves,gaskets, etc. are All Exactly the Same..... Only Much Cheaper...... Another advantage to the Carter style carbs.... There are NO gaskets or other potentail leak points Below the gas level...... 1 Solid Casting.... BTW, I've got a 351W, 1973, OMC,Complete Engine assembley setting outback, Without a home to go to...... It's got the Iron 4bbl manifold,+ Holley carb on it(OMC original).........

LubeDude · Nov 22, 2003

Re: Upgrading to a 4bbl Carb?

Bondo is correct in that these carbs are all the same, If Edelbrock is advertising a Marine Carb, thats probably the way to go!! I wonder what the difference is???? Thats also true about the power valve, its the metering rods that take the place of the power valve! The spring that controls that function is very easily changed from just under the air filter!! The roller rockers are a Luxury Item in my opinion, They will free things up but you will not see that much of an improvement in power( Seat of the pants)! and the RPMs that boat engine run, Unless you use a different retio: Not sure about that one, depending what cam you are using! LubeDude

Boomyal · Nov 23, 2003

Re: Upgrading to a 4bbl Carb?

Bondo, too bad you're away out there in NY, a 351w would be a dropin for my app. Lubedude, there are four possible differences in marine carbs. 1) they have a "J" tube vent for the float chamber to dump any overflow down the venturis. 2) they have "sealed throttle shafts to prevent any leakage out into the engine compartment. 3) they have a more corrosion resistant finish 4) some have a fitting to accept the diaphram rupture line from the fuel pump. My OMC uses a double diaphram fuel, w/ sight glass, instead. Sounds like Edelbrock may be the way to go. I can probably get them to suggest a good matching carb. manifold, cam set for my engine.

LubeDude · Nov 23, 2003

Re: Upgrading to a 4bbl Carb?

Thanks Boomyal: Now I know! Does make sence!! LubeDude

Upgrading to a 4bbl Carb?

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