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Old 09-24-2008, 08:15 PM
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Best CFM Carb for 350 checy?

I have a Stock 4 bolt main 350 chevy with a 700r4 and 392 rear gears in a Ford F1. What is the best CFM for a balance of power and fuel economy?

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Old 09-24-2008, 08:40 PM
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A Rochester Quadrajet.
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Old 09-24-2008, 08:48 PM
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Quote:
Originally Posted by DoubleVision
A Rochester Quadrajet.

Ditto--------------------!
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Old 09-24-2008, 09:47 PM
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times 3.......
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Old 09-24-2008, 10:32 PM
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Is that - Carb For Me, or Cubic Feet Minute?

I don't know, but if you don't like it this way


you could try something like this...

in a V8 version of course
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Old 09-25-2008, 03:04 AM
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Quote:
Originally Posted by lelshaddai
I have a Stock 4 bolt main 350 chevy with a 700r4 and 392 rear gears in a Ford F1. What is the best CFM for a balance of power and fuel economy?
Qjet always wins this question.
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Old 09-25-2008, 03:40 AM
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ok now to answer the actual question. he didn't ask for a brand by the way. i've found that a 600 is just about perfect for a 350. i've had a 600vac, a 750 vac, and a 750 mech, and the 600 vac was just as strong as the 750 mech. the only thing that i liked was the mechanical secondaries but a cheater screw DOES help on a vac secondary you just have a bog before the secondaries pickup (about half a second). anyway, i would shoot for a 600-650 and you will be happy. anything over 750 is really just overkill unless your doing hardcore 1/4mile runs with 15-1 comp and a 600+ lift cam. i ran my 600 on a 350 with 11.5-1 comp and a 510 lift 310 dur cam. and it hauled ***** (420 hp at the wheels) and tached to 7800 rpm before it even started to run out of steam. now here comes the **** storm of people telling me i dont know what i'm talking about.
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Old 09-25-2008, 09:31 AM
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The question was what was the best cfm carb for balance of power and economy and in that case you can`t beat a Quadrajet. The small primary`s are almost sensitive as fuel injection, give great throttle response with excellant economy. When performance is needed the massive secondary`s are there to give it all the flow it needs. Most Quadrajets flow 750 cfm, but it`s a air dam carb so it only gives what the engine demands. Sure, a 600 cfm carb would work, as would a 750. But his engine is stock, and he wants performance and economy and for a application like that the Quadrajet is the best carb I know of. I`ve used holley`s, demons, edelbrocks. But I always go back to Quadrajets.
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Old 09-25-2008, 10:00 AM
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Go to the Holley website and use the Interactive Carb Selector at the middle top of page, first off enter your CID.
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Old 09-25-2008, 10:02 AM
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" What is the best CFM for a balance of power and fuel economy?" ok? last time i check cfm stood for cubic feet per minute, not brand name. i never said go buy a holley or a edelbrock. i dont even have anything against quadrajets. he just asked for a good cfm to run on a 350 for power and economy. hence the 600 is as strong as a 750 (theres your power), its also inherent that the 600 will have better economy since it is a smaller carb. i do believe my self that the quadrajet's design would probably provide better economy in most situations, but to just tell him to buy a quadrajet isn't really answering his question. thats like if somebody asked what size tire goes on an 87 Mazda truck, and i said a b.f. Goodrich.
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Old 09-25-2008, 10:05 AM
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i like the AFB . its economical. super easy to work on. the secondaries have mechanical butterflies. there is an adjustable spring air door that supply resistance for the carb to pull off from. 3 holes for accelerator pump timmings. the step rod metering system is breeze to getting tune. works over long perios of time. edelbrock makes a thunder series that is nice.
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Old 09-25-2008, 11:15 AM
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Lookit, I didn`t reply out of having a pissing contest over this. He said stock, how many millions of GM vehicles came stock with Quadrajets? V6`s came with Q-jets knowing it would never use 750 of flow but thats the beauty of a air dam carb. In any stock application CFM pretty much doesn`t matter, you can bolt a 1 barrell on it and it would work one in the same. So I answered his Question by saying a Quadrajet and many agreed. It was the simplest answer without getting technical about it. Who wants to get technical over a stock engine?
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Old 09-25-2008, 12:10 PM
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Whoaa, guys... chill out. First of all, he didn't say if his "stock" 350 was 140 hp or 300 hp, so the answer could be 350 cfm or 600 cfm.

He asks a generic question, he'll get a generic answer. One of the reasons we all said Qjet was because (in addition to being a great carb) the way it meters flow makes it work over a wide variety of applications.

So, to say "you need 600 cfm" is pretty ridiculous since we don't know WHICH stock 350 he has.

Here's the math, assuming you have one of the millions of stock 350s that were in the 175-hp territory. It probably has 7.8:1 or 8.0:1 compression, wheezer heads that wimp out by 4500 rpm, and a sub-200-degree cam. So, a 350ci engine at 4500 RPMs and 80% VE consumes exactly 364.58 CFMs.

If you really want economy, get a 2bbl, or a Qjet. You won't give up any power, and you just might improve torque, throttle response, and almost certainly will improve MPG. Keep in mind that 4-bbl carbs were an old trick to get more power back when the largest 2bbl carb you could get was about 290 cfm, and the largest 4-bbl was 385 cfm. The need for 4bbls on a stock 350 is ridiculous, but the Qjet's primaries are just about ideal for anything.
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