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Old 05-28-2008, 06:40 PM
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carter AFB or Rochester Quadrajet?

i'm building a pontiac 428 with a fairly mild cam and mostly stock components, i've got a question about carbs...

i have the original quadrajet that came with the motor from the factory, and i have a carter AFB and intake that i came across. i'm not sure how to tell which one would be the better choice, i love the look and simplicity of the carter carb, but i know more about the quadrajet. how do you find specs on these carbs? and how do you choose which would be the best?

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Old 05-28-2008, 11:25 PM
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My vote is for the Qjet. Not only is it already set up for your 428, but its just a vastly more sophisticated piece. Carters aren't bad, but think of it this way... Edelbrock bought the carter design, improved on it some, and its still at the bottom of the sophistication totem pole.

Take a look also at the front of the Carter. If it has the two idle mix screws and then one big screw in the middle, its a little tough to compensate for modifications. The outer two control idle fuel. The middle one controls air. So, to set your idle speed you have to delicately balance all three. Many of them didn't even have an idle set screw. To change the idle you have to open up the air bleed, then retune the idle jets. I tried to make mine work on a slightly modded 389 and it just plain wouldn't idle above 500. Not good for the cam I had
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Old 05-29-2008, 06:26 AM
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Seems nobody likes the Carter/Edelbrock/Weber. I've used them with good results, along with Holleys and Q-Jets... If you don't get it dialed in (any one of 'em) you most certainly will not take a liking to it (whatever your choice). JMO
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Old 05-29-2008, 09:45 PM
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I have a 428 in my Catalina and went from a Holley that ran terribly to a carter AFB that ran much better and just switched to a Qjet. I don't have it completely dialed in yet but is seemed to run better. I got the Qjet used and don't know what jets or rods are in it. It started right up after I got it full of fuel. Right now it doesn't have the best performance on the road but with the change in linkage I am not getting full pedal because of carpet interference.

I need some more adjustment but I think the Qjet will be the better carb. I have not had any problems with the AFB and have not tried tuning it to the motor since it seemed to run so well as soon as I put it on. I learned a lot more about tuning when messing with my Chevy 350 that could be applied to the 428.
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Old 05-30-2008, 12:33 AM
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Quote:
Originally Posted by Stroke
Seems nobody likes the Carter/Edelbrock/Weber. I've used them with good results, along with Holleys and Q-Jets... If you don't get it dialed in (any one of 'em) you most certainly will not take a liking to it (whatever your choice). JMO

I have nothing against the Edelbrock except for its metering simplicity. It tends to take broad stabs at fuel metering; fine for the casual driver, but there is a reason serious racers use Holley and serious tourers often use Qjets.

The thing about early "air bleed" Carters is that they are darn near impossible to tune for anything but the stock combo. My 389 ran like a dream (other than wiped cam lobes). I rebuilt it with some 6X heads for 8.5:1 and an RV-type cam and there was no amount of tuning that would get that car to idle. There were NO provisions for idle speed adjustment, simply a cast-in tab that was a throttle stop. You adjusted idle with a large air-bleed screw in the middle of the front. It was fine for a stock engine, but simply not up to the task of working on even the most mildly modified engine.

I think Carters are easy to tune, and lord knows that Qjets aren't, but at least the Qjet offers a little more tunability
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Old 05-30-2008, 01:20 AM
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"I am not getting full pedal because of carpet interference."

Probably best to leave it that way with the price of gas.
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Old 05-30-2008, 09:08 PM
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Quote:
there is a reason serious racers use Holley and serious tourers often use Qjets
Sure, same goes for Dominator use on street set-ups. Those guys hate anything but. The Q Jet is no doubt a good carb. Holley has plenty for this app too, and Jet Performance has their
Quote:
800 CFM Quadrajet specifically built for modified Big Block Motors 396 cubic inches or larger. Jet can also rebuild your exsiting core to your vehicles specifications.
There you go, have one made for what you have.






I am not a compensated endorser or seller of any product.
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Old 06-01-2008, 12:40 AM
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I vote Q-jet. It'll make good power and you can't beat one for gas mileage. It's already devoid of hookup problems, jetting's probably close to ideal, and those old factory Q-jet intakes will outperform a Performer on the low end & and equal one up top.
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Old 06-01-2008, 01:24 AM
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Quote:
Originally Posted by jimfulco
I vote Q-jet. It'll make good power and you can't beat one for gas mileage. It's already devoid of hookup problems, jetting's probably close to ideal, and those old factory Q-jet intakes will outperform a Performer on the low end & and equal one up top.
All the cirlce track racers want the old Q-jet intakes with the numbers of 346246, (346249 - 305/350/400 75-77) & (346250 - 305/350 76-82) . Say those 3 flow the best of all the old factory Q-jet intakes. I think I still have 1 left, not sure which # I think the 246 or249.
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