500 cfm or 600 cfm
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Senior User
Joined: Jan 2003
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From: Calgary
500 cfm or 600 cfm
I am thinking of replacing the stock 2 barrel manifold and carb. on my '72 302 with an Edelbrock manifold and 4 barrel. My question is would a 500cfm carb be better for low end throttle response and gas mileage than a 600cfm. The engine is presently set up as follows:
Pertronix ignition
Headers/dual exhaust
Summit cam with 204º/.448", 214º/.472"
Stock low comp. pistons and heads.
Would I still get a pretty good kick when I open the secondaries with the 500cfm?
Thanks
Pertronix ignition
Headers/dual exhaust
Summit cam with 204º/.448", 214º/.472"
Stock low comp. pistons and heads.
Would I still get a pretty good kick when I open the secondaries with the 500cfm?
Thanks
Super Moderator
Joined: Apr 2004
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I had a 390 CFM on a 289 and the secondaries were always welcome.
If you do the math you can see a 302 running at 100% volumetric efficiency at 6000 rpm would pull 524 CFM.
Since you aren't running 100% VE, the 500 CFM carb should work fine, unless you plan to race. You will have better response and economy from the smaller carb.
If your going racing, go for the 600.
Put a balance tube between your duals as soon after the collectors as you can. This gives each exhaust pulse two paths and mellows out the sound.
If you do the math you can see a 302 running at 100% volumetric efficiency at 6000 rpm would pull 524 CFM.
Since you aren't running 100% VE, the 500 CFM carb should work fine, unless you plan to race. You will have better response and economy from the smaller carb.
If your going racing, go for the 600.
Put a balance tube between your duals as soon after the collectors as you can. This gives each exhaust pulse two paths and mellows out the sound.
Junior User
Joined: Sep 2004
Posts: 68
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From: washington!
I have run a 500cfm carter AFB on my 302 bronco for 6 years and it never gave me trouble and ran great. I also replaced the larger 4bbl that came with my 302 powered F-150 with a 500cfm edelbrock and its also performing much better than it used to. Though I usually stay out of the secondaries when they do come in it is noticable (especially since the edelbrocks/carters are spreadbore). These carbs are my mainstay for a 302.
Posting Guru
Joined: Mar 2004
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From: Destin/Ft. Walton Beach,
I've used 500 and 600 cfm Edelbrock carbs on a 302, and 600 Holley double pumpers and 670 cfm Street Avengers on engines with the same cam fordxxx is using. A 289 or 302 with a 600 double pumper, cam, headers, low gears and manual tranny, is a kick butt combo. An easy 1 hp per cubic inch. The only possible drawback to using the bigger carbs, is a little poorer gas mileage, and a little less low end torque. The bigger carbs (to a certain point) will build higher horsepower numbers. I don't care what size carb a 312 had, or whatever. The 302 Boss had a 780cfm carb stock. I'm not saying that was the correct size either for that engine. A Ford smallblock responds well to being "overcarbed" by "doing the math". I'm speaking from over 30 years of working on and driving Fords with a small block. Not from what I've heard from somebody else.
Last edited by stevef100s; Dec 12, 2004 at 10:42 AM.
Laughing Gas
Joined: Feb 2004
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most of us are speaking from years of work as well.i dont plan on running something that is wound up all the time so i stick to small carbs.
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Senior User
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From: Calgary
Yeah, as you can tell from my original post I am leaning toward the 500cfm carb. On bit of info I didn't put in my original post is that I have a C4 automatic with stock converter behind that 302 so that makes me lean a bit more toward the low end torque.
I was thinking of swapping that stock converter out for a slightly higher stall unit but that is another story...er post.
Thanks for all the input.
I was thinking of swapping that stock converter out for a slightly higher stall unit but that is another story...er post.
Thanks for all the input.
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Originally Posted by stevef100s
I've used 500 and 600 cfm Edelbrock carbs on a 302, and 600 Holley double pumpers and 670 cfm Street Avengers on engines with the same cam fordxxx is using. A 289 or 302 with a 600 double pumper, cam, headers, low gears and manual tranny, is a kick butt combo. An easy 1 hp per cubic inch. The only possible drawback to using the bigger carbs, is a little poorer gas mileage, and a little less low end torque. The bigger carbs (to a certain point) will build higher horsepower numbers. I don't care what size carb a 312 had, or whatever. The 302 Boss had a 780cfm carb stock. I'm not saying that was the correct size either for that engine. A Ford smallblock responds well to being "overcarbed" by "doing the math". I'm speaking from over 30 years of working on and driving Fords with a small block. Not from what I've heard from somebody else.
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Senior User
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From: Calgary
Merry Christmas everybody. Guess what I got for Christmas...a new Edelbrock performer 289 manifold and Edelbrock 600 cfm carb. My son and wife bought it after a lot of hinting from me. So I am going with the 600 cfm after all and I'll let you all know how it works.
My existing setup is a manual choke which I like very much but the new carb has an electric choke. I have no experience with these...are they good, any advise on setting it up?
The stock manifold bolts are a little too short for the new manifold so I went to the hardware store and bought longer stainless steel one and washers. I figure with the aluminum I should put flat washer under the bolts. Comments?
Thanks
Thanks
My existing setup is a manual choke which I like very much but the new carb has an electric choke. I have no experience with these...are they good, any advise on setting it up?
The stock manifold bolts are a little too short for the new manifold so I went to the hardware store and bought longer stainless steel one and washers. I figure with the aluminum I should put flat washer under the bolts. Comments?
Thanks
Thanks
Elder User
Joined: Nov 2004
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From: So. California
ON a 302 with a 220/230 cam can you gain any torque around 1500-2500 with a 600+ cfm 4 barrel?
I aknow from looking a edlebrock dynos and hp calculaters that a 302 can make 275lbs at 2500 easy and a 351 is around 2500, I have heard of a 400 making 456lbs of torque at 2000 rpm, that is about 1.5 ft/lbs per cubic inch.
So mabe with high compression 340 ft/lbs whith 302 and 394 ft/lbs with a 351 is possible with overcarbing and mid size cams.
I aknow from looking a edlebrock dynos and hp calculaters that a 302 can make 275lbs at 2500 easy and a 351 is around 2500, I have heard of a 400 making 456lbs of torque at 2000 rpm, that is about 1.5 ft/lbs per cubic inch.
So mabe with high compression 340 ft/lbs whith 302 and 394 ft/lbs with a 351 is possible with overcarbing and mid size cams.
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