carb size

This is for you guys who are always asking abour carb size. Don't be wondering why your mileage goes to hell after you install that 650 CFM Edelbrock AFB

"This is a question I get asked a lot. What carburetor would be best for my engine? Whether it be a 1, 2, or 4 barrel, here is a little help for you. There is a formula that will get you very close to the proper cfm for your engine. The formula goes like this:

cubic displacement divided by 2 (ex: 3515.5)

maximum rpm divided by 1728 (ex: 6000 rpm=3.47)

multiply those two figuires (ex: 175.5 x 3.47`8.98 cfm)

Hold on we are not done. You now have to factor in volumetric efficiency. A Nascar race engine runs at 85%-90% volumetric efficiency. A normal street car wil be 75-80%, depending on what you have done with your heads and exhaust.

Ex: 608.98 x 75%E6.74cfm

With carburetors, bigger is not better. You will not get very good results with an 850 double pumper on your small block Chevy. If you are after good idle quality, fair fuel mileage, and good performance, stick with this equation. The boys at GM and Ford used this equation for many years and it works! You can not change the laws of physics. I would like to thank Jon Enyeart of Pony Carburetors for teaching me how to properly restore and install a carburetor. He is the Grand Wizard of carburetion."

Kurt Praxl

Kp Carbs

Reply to
dwcars
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Reply to
Pat Drnec

How timely, I was just looking at the Edelbrock web site on carbs. Wondering if they have a 500cfm that would replace the WCFB on my '54

232 coupe. It has the '55 President manifold, Carb and air cleaner. The WCFB runs good but sure gives me fits on hot restarts. Also the bowls dry out when it sits.
Reply to
Gordon

Reply to
Pat Drnec

Reply to
Pat Drnec

I have the 1403 on my '63 Cruiser. It's a 500 cfm carb and it runs great.

Chip

Reply to
cjdaytonjrnospam

Reply to
Gordon

there was a 4 bbl. flange to dual webers (horizontal mounted) with neat twisted tube design, also could use dellorto carbs.

Reply to
oldcarfart

To all of the folks running an internal combustion engine with too big a carburetor that "runs just fine" or "runs great"...

What do you base this on?

If you've never run the same engine/car with different size carburetors and actually taken the time to find the correct tuneup for each carb. size....you have no basis for saying "it runs just fine", or "it runs great".

Fine and great are VERY subjective adjectives. But without other information...maybe...just maybe, something else just might run better !

There are three or four different methods for finding the "correct" carburetor size for your particular engine size "and" it's intended purpose. They are all very close to the same...within about 25 /

35cfm.

Now you say (none have so far!), what about the Chevy and Ford 302 of the late 60's? they both had 780cfm carburetors on them ! Yes they did. The were the correct "combination" of parts that yealded a fairly high rpm engine. Both of those engines loved running down the freeway at 4000 rpm. I know I had the daily use of a good running 69, Z-28 Camaro...with the 780 Holley (though it was listed in Chevy books as an

800cfm). Funny too...neither of those engines got much for milage!

Do most small cu. in. Stude drivers have 3.70 and lower gear ratios...probably not, do most Stude engines have a cam that lift's the valves over .465 gross lift, probably not, larger thAn 2.00" intake valves, angin, most likely not. I'd also bet that the worst flowing Chevy or Ford head in the late 60's flowed better than most Stude heads...some that have even been ported!

So...back we go the formulas. I've messed with carburetors and spacers for a long time, time enough to know that if you want the best from a stock to moderatly modified Stude engine...stay with what the experts suggest...500 cfm. Will a mildly modified 289 Stude engine run just fine with an 800 cfm Holley...that's tuned right....yea. But not as good as it would with a smaller carb. siting on the manifold.

This doesn't apply to drag race or Bonneville...flat out type "combinations" ! Even the engines for racing only...small engines will work just fine without resorting to two Dominator (Holley) carburetors!

Mike

Reply to
Mike

I guess all of us running 600 cfm Edelbrock 1406's on 289s are wrong. I guess that I must be kidding myself when I think I'm getting 22+ mpg on the highway in my '61 Hawk. I ran the original carburetor for the first year, until even after a rebuild I was only getting around 14 mpg. I don't see any reason to run out and buy a 500 cfm carburetor to put on an engine that's running this good.

Lee

Reply to
Lee Aanderud

I routinely get 25-26 mpg in the PowerHawk with a 2bbl Stromberg...

JT

Lee Aanderud wrote:

Reply to
Grumpy AuContraire

Was gonna, but you took the wind out of my sails.

Reply to
Dave's Place

You tell me. I had the carburetor adjusted by a knowledgeable Studebaker guy, an old time garage (who also did the rebuild) and f***ed with it myself. The Edelbrock I took out of the box and dropped it on the engine and have been running it without turning a screw since.

Now go take your blood pressure medication.

Lee

Reply to
Lee Aanderud

Reply to
satdoc2 via CarKB.com

Reply to
itraseecab

You would be amazed how well the webers work in a blow thru application. My son runs one with only a sealed box taking the place of his air filter.Used on his 1641 cc drag VW bug(100 cubic inches-6.48 @ 106 MPH in the 1/8 mile runs) This setup was used in a street car for a year,before it went full time racing. 20 psi boost..

Freddy

Pat Drnec wrote:

Reply to
Freddy Badgett

I had a 352 Ford PU one time, milage SUCKED.. factory Ford carb 2 b.. got 9..

and I got tired of it, and talked to a guy.. bought an adapter plate for a quadrajet.. and REJETTED it.. took most of an afternoon.. took the primaries from 105 down to what it would run on.. which happened to be .055.. changed the secondaries down from 140's to .060's..

got 19 MPG at 70 MPH then..

now, if I WERE to find a DECENT quadrajet, no matter the size, as long as the primary and secondary plates were CLOSE to the same size I would put it on my 289.. and MY rear end SUCKS big time.. its a 2.42 the best we can figure..

but, we got a guy in the local club that can get a bit over 26 mpg on his 289, 3sp and OD, driving it at 60-70 mph..

--Shiva--

Reply to
me

A local repair shop owner does a car talk radio show on Saturday mornings. His shop has a chassis dyno and does a lot of performance work. Just last Saturday a caller asked him about installing an Edelbrock on his Camaro. Tom told him that compared to the Quadajet already on the car, the Edelbrock was junk!

Reply to
Dwain G.

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