How to Identify Quadrajet

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How to Identify Quadrajet

Postby hammerdown7 » Mon Nov 22, 2010 11:35 am

I have a used Quadrajet that doesn't seem to have any numbers on it. The only one I can find is a '149' stamped on the bottom with a couple of unreadable marks before the '149'. How do I find out what it is?

Dick
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Re: How to Identify Quadrajet

Postby 3pedals » Mon Nov 22, 2010 12:18 pm

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Re: How to Identify Quadrajet

Postby hammerdown7 » Mon Nov 22, 2010 12:44 pm

Thanks, I've checked out that site as well as others but they are all keyed to deciphering numbers and the one I have has only the ones on the bottom. Haven't been able to find how to measure it for ID either.

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Re: How to Identify Quadrajet

Postby 3pedals » Mon Nov 22, 2010 1:22 pm

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Re: How to Identify Quadrajet

Postby cammerjeff » Tue Nov 23, 2010 12:26 pm

You probably have an early 66 or 67 Q-jet, those years used a round stamped tin plate that was glued onto the left side of the carb main body. There will be a round cast in indentation in the housing were the plate would have been. Most of the time it either has fallen off and lost, or was removed during a previous rebuild during the soaking process and not reinstalled. I do not know a way to ID a Q-jet missing this plate. Here is a video I found that shows the plate location well. Good luck on you ID. If it is a 66 or 67 it is a 750 CFM model, the only size they made those years. If it is a 800 CFM model you can ID it by opening up the butterfly valves and looking at the primary bores. If the bores are round it is a 750 CFM, if the bores each have a small bulge towards the center of the carb (and a little to the rear) it is a 800CFM model. They increased the size by increasing the primary bore size, the secondary bores are the same size. The bulges are requires to keep the float bowl size the same as the larger primary bore intrudes on the float bowl space.

Just FYI I have not seen a 76 or later Q-jet that was not a 800 CFM model, and most 800 CFM carbs will have a integral choke assembly either with a hot air or electric ciol assembly. They did make a few 800 CFM carbs 70-75 mostly on large Buicks & Cadies (and a few HP pontiacs like the 71-72 455 HO & 73-74 SD 455's), and the early ones will have a divorced choke with the coil attached to the intake manifold. I used to sell those for some good $$$ to racers in the early 80's as they can easily be made to look stock. The only exeption to this are the 80-85 4.1 Buick V-6 Q-jets they are smaller around 580 CFM. Hope this helps. Pic's would clear this up.


http://www.youtube.com/watch?v=9Ya2-R60akw
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Re: How to Identify Quadrajet

Postby hammerdown7 » Tue Nov 23, 2010 2:06 pm

Thanks Jeff,
This carb does not have the round cast area where the stamped plate would be, it is flat in that area. The carb looks very similar to the one shown in the video. I can't see down the bores clearly with the butterflies in place. It's used, I'll try and clean it up for pictures. It has been sitting on a shelf for some time.
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Re: How to Identify Quadrajet

Postby monzajer » Tue Nov 23, 2010 2:12 pm

Jeff, nice job in desribing the Q-jet! :th:

I would like to add, for those that are new to the carb or just would like a friendly reminder---not ALL Q-jets are the same. They made some subtle differences in the way the carb came apart. And some of the screws, like the butterfly screws can snap, if you are not careful. Be sure to look on bottom side of plates to see if anyone staked this screws so they wouldn't back out. If they are staked and you try to just unscrew them, they will most likely break leaving you with a WT... feeling.

In addition to what Jeff provided there is a very good manual by Doug Roe on this type carb. All SORTS of good info!!!

Here it is: http://www.amazon.com/Rochester-Carbure ... 0895863014

There are others out there, as well.

Jeff said, he "...used to sell them to racers back in the '80s." They are very good carbs, if you know what you are doing.

We used them to run 327, 350, 400, 377, 383, etc. in the roundy-round cars and they worked great. 750 CFM can provide enough for many size engines, including big blocks.

Many kits you buy at your local Checkers, O'Reillys, etc. have pieces for different ID number carbs in the same kit. So, if you can get a number from a similar carb, chances are, you can make it work. Most components in these kits are the same, but they did make some changes to gaskets. Keep a very good eye out for that, and different gaskets are provided in the kit. Rochester/Carter did make many changes over the life of the carb so very similar carbs are necessary to have a better chance at a kit match.

Like Jeff said, pics would be good. Maybe someone here has a carb like yours and can help with an ID number. Shoot I think I've have or had 5 or 6 Q-jets sittin around here. Now, where did I put those? :lol:

Anyway, provide a pic and go from there.

Good luck and have fun.

cheers jer :mrgreen:
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Re: How to Identify Quadrajet

Postby hammerdown7 » Tue Nov 23, 2010 2:34 pm

Thanks again, an area I thought was clean behind some of the linkage was just dirty enough to cover the number, 17057213. Found one on eBay that said it is a 750 CFM for 76-78 Chevy, Chevelle, Nova & Camaro.

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Re: How to Identify Quadrajet

Postby cammerjeff » Tue Nov 23, 2010 9:40 pm

Dick,

My books show it as a 800CFM from a 1977 Chevy or GMC truck off a 350 SBC
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Re: How to Identify Quadrajet

Postby chevy art » Tue Nov 23, 2010 11:18 pm

just a little info on the qjets. they can be made to do unbelieveable things on race cars. a guy named hedreth does the qjets for the nhra stock and superstock racers, my buddy runs a 68 camaro ib SSG 350 cubes, 290 horse with the small chevy steel heads(190 intakes, not the 202s) 10-1 compression, any cam you want and any intake(you need to run the original carb(qjet) and he runs besrt et of 9.81 seconds in the 1/4 mile. cant never sell the q-jets short. art ps hedreth gets about $12oo for a race ready carb
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Re: How to Identify Quadrajet

Postby spencerforhire » Wed Nov 24, 2010 7:36 am

Val Hedworth(to correct Art's spelling) is the widely accepted Quadrajet(and other Rochester carb)guru, and has been building Q-jets for at least 30 or 35 years; I think I remember seeing his name in the NHRA Stock and S/S Eliminator record books back in the 1970's.
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Note- the very act of listing all of these has made me realize I have some kind of problem.....

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Re: How to Identify Quadrajet

Postby chevy art » Thu Nov 25, 2010 2:37 pm

spence what could he possibly do to those carbs to make them so good and expensive. my buddy with the camaro(in the 9s) has 2 of them. one for reg days and one for real hot days. art
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