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which carb to get?


Well-known member
Hey guys I got a question, on my new boat I have a 350 out of a 82 vette and there is a Holley 750 double pumper on it. Since I am running dd and my engine doesn't really go past 3200 I don't think I need a 750. Should I get a 600 double pumper? Or how about one with vacum secondaries instead, what's the verdict on those for this application? I have never ran a Holley on anything however I ran an Edelbrock 1405 600 cfm on an AMC 401 in my old mud truck and it worked great but all I hear is Holley, so what should I do? Thanks. :?:
I can't remember the math but it goes something like (rpm, cubic inches, gives you CFM). Anyway you could feed that small block with ease, using a 500 CFM carb. You do not need a double pump carb at all. I have seen so many people pour to much fuel into a direct drive motor trying to make more power . If you have to much fuel you will wash your rings and end up with snow coned cylinders.
I'll check the plugs tomorrow. what about a 500 2 barrel? Or should I stick with 4? Looks like I'll be in the market to trade this 750 double to some one with a 600 vacum secondary model. Any takers? :) :) :)
here is your formula

The formula is: Engine Size (CID) X Maximum RPM / 3456 = CFM @100% Volumetric Efficiency

Example: 350 CID X 6000 RPM = 2,100,000 / 3456 = 608 CFM
I did the formula for a 3100 rpm max and came up wiyh 313.94. closest thing to that is a 390 holley I believe. Hey WaterThunder, care to chime in with some infinate wisdom. Any one out there ever run a 390 an a dd 350 before?
A buddy of mine is currently running a 500 2 barrel holley on his dd 400sb. He says this is his best setup to date, he's been through a couple diffrent 4bls and likes this setup. In the past I know a popular carb to run on dd motors was the holley 4360 economaster quardrajet replacement. It is a 450cfm mech sec. 4 barrel that ran great on dd mototrs ranging from the 300 buick to 500 caddy's.

wow, a 700 holley 4 barrel, to a 500 2 barrel. Big difference. my motor runs good with the 750 but I don't want to wash the rings. Hey Thunder and Felbr what do yall recomend? I am still no closer to picking something else.
I run a 500 Edelbrock on my dd 383, works great

Excellent fuel economy, excellent throttle response and I didn't have to use an adapter to put it on my intake.
I run a 500 Edelbrock on my dd 383, works great

Excellent fuel economy, excellent throttle response and I didn't have to use an adapter to put it on my intake.
In a DD application a 500CFM 2 barrel is very hard to beat with a small block! If you wanted to run a four barrel a 600DP is as far as you would want to try! Stay away from formulas when calculating carburetor sizes for an airboat! Me personally I would try an air-gap dual plane manifold with one of those high dollar 4 to 2 barrel adapters the circle track guy's use. You can make big power with that combo but still have snap! There are a lot of very nice 2 to four barrel adapters for the limited late model and late model guy's!
A 750 is to big for a DD 350. You could try disconnecting the secondaries but then it might be a tad too small!
Hey if you can get me pics of your 750 and throttle shafts are good and it's nice I have a never been gas through 600 double pumper. Can do the same with pics! Don't think i will use it as I just built a 850 4 corner idle but 750 might be somthing to work with. Shipping would probably be about $25.00 ea. Pretty carb! :wink: