Debate on carb size on my 351 cleveland

[Eliteman76]

I have a bit of dilemma on the size of the carb on my 351c in the GTS.
For some time now...its been nagging me I "think" I need to step to a slightly larger carburetor. In discussing with a good friend, he thinks I should go for a 600-650 Demon, or step to a larger Edlebrock carb. I was told the 600 CFM performer is probably choking the engine some.
Now, as most of you guys know, I am a street car guy, not some racer. Granted I like to really drive the GTS, but with the 2V heads, I have decent movement for what I have set...but I think at times, that car needs more carb.
Looking at the engine speed, where it typically resides, what I get is around 609CFM from a couple calculators I have done.

I've been pretty content with the 600, I have the 1406 on the GTS, and the 1405 on my F150.

Think the 750 would be overkill?

And, because I'm in the market, anyone happen to have a 750 CFM performer collecting dust? ;D

[SpiderGearsMan]

Re: Debate on carb size on my 351 cleveland

heavy car ? automatic ? 3310 vac sec

[SpiderGearsMan]

Re: Debate on carb size on my 351 cleveland

it is only air , it's the fuel curve you have to sweat

[Ron Ward]

Re: Debate on carb size on my 351 cleveland

heavy car ? automatic ? 3310 vac sec

Bingo! Spidey nailed it.

3310-1 to be exact. Drop leg boosters, secondary metering block, large vaccuum port at rear of throttle plate for power brakes....

Ron

[Barry Donovan]

Re: Debate on carb size on my 351 cleveland

is that solid tap engine?

make it strain. 650 can be a slob..750 is an obese heart attack.

I can see why you would like 600 on that engine.. I would not give it up, if its good.

[Ron Ward]

Re: Debate on carb size on my 351 cleveland

Boxer,

A 3310-1 (or any 3310 variant) can be fitted with different springs in the secondary diaphram to regulate opening of the secondaries. I have a quick change cover on mine that takes all of 30 seconds to change the secondary opening rate from street to strip. A 750 vaccuum secondary (or 780 for the 3310 & 3310-1) is not too much for a 2V Cleveland.

[JeffMcKC]

Re: Debate on carb size on my 351 cleveland

Edelbrock Q-Jet Carburetors on a daily driver, best of both worlds and very tuneable big plus is no power valve to leak. Plenty of carb for most Street cars and get great mileage too

[A/Fuel]

Re: Debate on carb size on my 351 cleveland

Boxer,

A 3310-1 (or any 3310 variant) can be fitted with different springs in the secondary diaphram to regulate opening of the secondaries. I have a quick change cover on mine that takes all of 30 seconds to change the secondary opening rate from street to strip. A 750 vaccuum secondary (or 780 for the 3310 & 3310-1) is not too much for a 2V Cleveland.

I have a couple of 3310's that I've screwed around with that I think are good street carbs. I've added a scondary metering block, even though you can change the plates, I think it's easier to just change jets. Especially if you have a bunch of jets already. I have an open plenum intake and found that a 50cc pump works good and can use a .042 discharge nozzle, along with the lighist spring (i think is a yellow) It probably shouldn't work, but I like it.

This is on a very mild 350, has good low end and revs to 6500 pretty easy. Gas mileage is pretty good, i don't have current numbers but it gets around 12 mpg, I think that's pretty good for 5.13 gears. I can usually get over 100 miles out of 8 gallons and that's with numerious blasts to 100mph a night, lol.

[Tazracing]

Re: Debate on carb size on my 351 cleveland

I know this will hurt, as your a ford guy..
but, a 780-800 cfm q jet.. will be best..
great all around mpg and big @$$ sec. when you need it..
or if motorcrap.. a 400m vac sec carb..
only thing a holley vac sec has over a q jet is bowl size.. and I'm willing to bet ,in your case isn't a factor
your 600 is to small ..
around 700 vac sec holley or 800 cfm q jet..
you can get away with the bigger cfm q jet as the primaries are small . and it acts like a smaller carb till you open the sec.
is there a intake spacer that take a q-jet.. if so.. you might try it.
good luck

p.s. j/y q jets in 800 cfm look caddy. or 350 trucks. and are cheap, and a r&r kit is cheap...
for 65 buck or less you can be running it and testing, and if it not work for you , you can get the money back selling it..

[Tom Slick]

Re: Debate on carb size on my 351 cleveland

It doesn't hurt a Ford guy. They put Quadrajets on CJ 429's.

[TC]

Re: Debate on carb size on my 351 cleveland

I firmly believe that any 350 cubic inch motor that has any performance mods done to it(cam, heads, etc....) should run at least a 750cfm carb. To me 600's and 650's are for stock type motors or 4x4's where low end torque and gas mileage is the main concern.

[SpiderGearsMan]

Re: Debate on carb size on my 351 cleveland

q jet has an emulsifier [power valve ] hooks the primary metering rods - APT screw on the early 80s ones

ditto on the q jet for a cruiser
I prefer holley

[Scott Liggett]

Re: Debate on carb size on my 351 cleveland

Edelbrock 750's are overkill for 350/351's if they are mild builds. They increase the primary side over the Eddy 600's to get the extra 150 cfm. So the part throttle response is drowned.

The Edelbrock 600 is great for all kinds of driving except full throttle runs. It'll run out of air and the car will nose over before you get 5000 rpm. But, you will have great part throttle response.

Holley's 750 vac sec would be great. Put a one step heavier spring than box stock for your heavier car and your set. If you want to go double pumper, you can get away with 650-700 easily and be very happy. A down jetted secondary 750 dp would work as well, but you wouldn't notice the difference until you were above 4500 rpm.

[63 falcon]

Re: Debate on carb size on my 351 cleveland

:o I am using the Summit 600 with Holley parts , works great . The 351 would probably work great with the 750 Summit.The reason I changed was the draining issue with the Edelbrock.

[SpiderGearsMan]

Re: Debate on carb size on my 351 cleveland

keep the eddy afb at 3 psi and all is well

the summit carb is nice simple old autolite/motorcraft 4300 update