Carburator size question

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The Blurr
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Carburator size question

Post by The Blurr » Wed Mar 07, 2012 11:17 pm

What size carburator should we use on a stock 500 cadillac engine with ederbrock performer intake and headers with 1.73 stringer 78" falcon 3bld on a 13.6 cottonmouth 3920 rpm at wot. Thanks Brent

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JAMES
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Re: Carburator size question

Post by JAMES » Thu Mar 08, 2012 7:20 am

carbs are always a big thing if u look up the info other then SA u will find it dont take many cfm;s to run the caddies the q-jet was a pretty big carb .. if i built a geared cad id run around 600-700 different srokes for different folks call ed mac and talk with him also pm PEOPLE THAT HAVE RAN THAT GEAR AND PROP WHICH THEIR ARE ALOT AND ASK THEM ... DO A SEARCH THIS IS JMO I RAN A 500 CFM ON MY DD DIDENT CARE FOR IT REBUILT THE 750 VAC SEC. AND LOVED IT AND GOT BETTER MPG
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Re: Carburator size question

Post by undicided » Thu Mar 08, 2012 3:10 pm

I recommend calling Holleys tech line, they are very helpful in sizing carbs

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John Fenner
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Re: Carburator size question

Post by John Fenner » Thu Mar 08, 2012 3:44 pm

500 Ci.x 3920 = 1960000 Divided by 3456= 567.1 A 600 Holley will be perfect!
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air-roberts
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Re: Carburator size question

Post by air-roberts » Thu Mar 08, 2012 4:05 pm

at minimum a 750 double pumper with 80 primary and 90 secondary airboats use alot more that people think but Read your plugs especially #7 that one seams to run the leanest. my buddy runs a 830 hp series and it's perfect
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MYDIXIEWRECKED
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Re: Carburator size question

Post by MYDIXIEWRECKED » Thu Mar 08, 2012 4:53 pm

I wouldn't neccessarily go with the first answer you get either. Do some research! I have a 364ci LS motor and I run a 830cfm... And I beg you to show mw a carb that will do better! :lol: I had Ed Macyntyre her in Lauderdale Tune it and wow it runs like it's fuel injected, no hesitation, doesn't load up either!
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John Fenner
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Re: Carburator size question

Post by John Fenner » Thu Mar 08, 2012 10:16 pm

JAMES wrote:carbs are always a big thing if u look up the info other then SA u will find it dont take many cfm;s to run the caddies the q-jet was a pretty big carb .. if i built a geared cad id run around 600-700 different srokes for different folks call ed mac and talk with him also pm PEOPLE THAT HAVE RAN THAT GEAR AND PROP WHICH THEIR ARE ALOT AND ASK THEM ... DO A SEARCH THIS IS JMO I RAN A 500 CFM ON MY DD DIDENT CARE FOR IT REBUILT THE 750 VAC SEC. AND LOVED IT AND GOT BETTER MPG
Not to start any ill discussions, but I would guarantee that the secondaries never opened 1/8th of the way ever on the 750 and the reason you got such good response and mileage was due to the fact you were basically running on 375 CFM (primaries) most of if not all of the time.
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Re: Carburator size question

Post by flying fish » Fri Mar 09, 2012 9:28 am

A holley is not a plug and play piece. The secondary spring can be tailored to meet the requirements of the application. Atleast I think this is the way it works. Short Yellow would be a thought. Then even a bit of tailoring to the short yellow if one chooses.

CID x max RPM X VE / 3456 = minimum cfm required. This minimum cfm is in no way maximum cfm one can use.

If your secondaries don't open completely @ WOT. Tune em till they do. I again think this is how it works.

It is also about the torque. minimum CFM required usually does not obtain max torque.

With a larger carb, sometimes a bit of manipulation to the idle circuitry, midrange tune, and WOT tune is also required.
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