quadrajet

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Zorm
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quadrajet

Postby Zorm » Thu Aug 02, 2018 5:39 am

has anyone ever run of these carbs on a non-cheby engine and have it run well?
Last edited by Zorm on Thu Aug 02, 2018 7:13 am, edited 1 time in total.
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tgreese
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Re: carter quadrajet

Postby tgreese » Thu Aug 02, 2018 6:22 am

What is a Carter Quadrajet? The Quadrajet is a carburetor made by Rochester. A Carter AFB 4V is different; it's the Edelbrock carburetor today IIRC.

The Quadrajet used to be a very popular upgrade for Wagoneers. It's a tapered needle carb, and has a reputation for being hard to tune. Apparently there are early QJets without electric servos (?) that are the classic hot rod Quadrajets. Lots of info about this topic online.

I expect the QJet for a Wagoneer has been replaced by TBI, which has become easy and common today. Should be plenty of discussion of the QJet in old posts at IFSJA.
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ProTouring442
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Re: quadrajet

Postby ProTouring442 » Fri Aug 03, 2018 5:15 am

Carter made Qudrajets under contract because Rochester couldn't keep up.

The Q-Jet is a great carburetor, and will work very well with a bit of tuning. For obvious reasons, you'll want a pre "CCC" (Computer Command Control) version. Do some research through Google and you'll find a lot of good information on their quirks.

I'd pick one from a similar displacement GM engine and go from there (they came on all GM engines, from the Pontiac Sprint-6 to the Cadillac 500).

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Cecil14
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Re: quadrajet

Postby Cecil14 » Fri Aug 03, 2018 7:18 am

The biggest issue I found with Q-Jets is worn throttle shaft bores. The body of the carbs are made from a relatively cheap aluminum, and the steel throttle shafts wallow out the holes in the housing over time, causing vacuum leaks. Lots of people have bore the holes out a little bit and used brass bushings, solving the problem.

The other thing that'd be an issue for most of the people here is actually bolting one onto a factory 4bbl intake. The Q-Jet is a spreadbore like the MC carbs we got, but it's a way different pattern. It can be adapted, but I don't know of any off-the-shelf adapters. If building your own, make sure you don't occlude the holes on either the carb or the intake.

As mentioned, there's a ton of good info about them around the internet and several great books on the topic. They DO take some tuning to get right, but it's not all that difficult, just some trial and error. The biggest problem there is having a pool of jets and rods to swap around.

If you do go looking for a used one, try to find one with as little play in the throttle shaft as possible.



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Herk
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Re: quadrajet

Postby Herk » Fri Aug 03, 2018 5:24 pm

Throttle bores can be repaired. The thing that turns most Quadrajets into junk is people over tightening the front two bolts and warping the crap out of it. Most of the tuning "problems" are due to warped bodies or idiots thinking that they can somehow improve it by making changes. The newest non-electric Q-jet is about 40 years old, so good luck finding a decent one. Or do what GM did: TBI.

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kansasboy001
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Re: quadrajet

Postby kansasboy001 » Sat Aug 04, 2018 7:54 pm

The edelbrock qjets are a good option they were made new from the mid 90s to like 2007 or something so theyre quite a bit newer than the original gm ones. I have a edelbrock 1904 on mine and it runs great. Only thing I did was swap secondary rods with CH rods to get rid of a stumble on wot. Not terribly hard to adjust once you realize that it does things a little diffrent than a holley or Carter afb. Read the gm tech book on them and the lars papers and you'll have a pretty good understanding.
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