carb thoughts

[Zorm]

I know this has been asked TONS OF TIMES. Don't need carb help but what is the cfm in the stock 2bbl carb on a 360? I bought a 79 and it has a 350 cfm Holly 2bbl on it.

I ask because is that too small for a non-modified 360?

[wiley-moeracing]

it's a little small. will work and give slightly better fuel mileage but you would be better off with a larger carb.

[tgreese]

The factory did not supply that info. You can guess from the CFM rating of similar carburetors and their CFM rating. Look at the venturi diameter of a Holley 350 CFM 2V and compare to the area of a Motorcraft. Some research and arithmetic is all that's needed. It'll be a WAG though.

Is 350 too small? No, I would say not. The trade-off is between fuel control and performance. A smaller venturi restricts flow more (less power at WOT) but gives more vacuum which better controls the fuel mixture. Larger goes the other way. A big carb on a small engine must be set up rich to compensate for poor control.

The 2300 Holleys are lousy economy carbs regardless, IME. 2100 and 2150 are much better.

[tgreese]

Extensive research determined that the 0-7448 Holley 350 CFM model 2300 carb has a 1 3/16" diameter venturi, or 1.1875. The two most common Jeep Motorcrafts are 1.08 and 1.21.

Area of each venturi is (diameter/2)^2 * pi. The area changes by the square of the diameter, so we can find (1.08/1.1875)^2*350 = 289. Or (1.21/1.1875)^2*350 = 363. Not far off, assuming the booster venturis and such are roughly equivalent.

http://www.crankshaftcoalition.com/wiki/images/1/18/HolleyCarbList.pdf

[Ristow]

the 1.08 is 287 cfm.


the 1.21 is just over 350cfm. can't recall the exact figure.

[FSJunkie]

The 1.21 venturi Motorcraft 2150 is rated at 351 cfm. Ristow was within 1 cfm.

I have a 360 with that carburetor and I have another 360 with a 600 cfm four barrel. The extra flow of the four barrel is really only beneficial above about 3500 RPM so it's not used very often. It helps you go faster when you downshift, wind it up, really stomp your foot down, and want all the power she's got to give....but its not something you use every day and you can get along just fine without it.

There is also something to be said for the simplicity and reliability of a two barrel carburetor. Four barrel carburetors in my experience are always more work to maintain.

[Cliff]

In the 70's the Holley 350 and 500 2-barrels were considered performance carbs for 6's and small V-8's. That was the thinking among gearheads anyway. I ran a 500 on my 304 Javelin for a few years because I couldn't afford a high-rise manifold and 4-barrel. It worked very good, even with my no-nothing tuning. For a stock 360 I would expect the 350 to work good - even better with tuning.

[rang-a-stang]

Nothing a turbo wouldn't fix...