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Is there any reason a '74 Qjet runs rich in a '72 chevelle?

2K views 6 replies 5 participants last post by  jasonh 
#1 ·
I am driving a 1972 El Camino 350 V8. The carb I took off was a '72 Qjet #70422100812.
I replaced it with a rebuild carb the parts store listed as compatable. When setting the carb I discovered I cant get the car to stall even with all the screws turned all the way in. The carb is too rich for my car. The numbers start with #7044 which means it is a '74 Qjet. I took the carb back to the parts store and told them to give me a '72 Qjet #70422100812. They said no problem we got one in stock and gets me another carb. I look at the numbers and its another '74. The computer lists a general number for Qjets that includes different years. Now either the carb was rebuilt incorrectly or a '74 is different than a '72. I dont know but I am thinking of rebuilding the old carb and then returning the '74. Any ideas will be much apprieciated.
 
#2 ·
Take the carb back. If you have a Pep Boys near, they sell rebuilts done by of all folks - Holley. I put a Holley rebuilt Qjet 7042202 on my 72 307 with Performer intake. It ran perfect out of the box. The numbers out of my 72 shop manual are as follows:
72 auto Federal qjet - 7042202, Calf. auto 7042902. Manual federal - 7042203, Manual Calf. 7042903. Those numbers are for a Chevelle. They don't show any for the Elk. I also have a 74 shop manual so I can reference those numbers. Remember that the 74's had much more stringent emmissions calibration. If you can't find a correct rebuilt you could either try to do it yourself or send the carb to someplace like the Carb Shop and let them do it. That way, you'll get yours back. Hope it helps.

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Tino #28 Gold
 
#3 ·
could they have given you a larger quadrajet for a larger engine? Could have larger jets and/or metering rods.

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70 chevelle ss396 conv
66 chevelle ss396 hdp/conv
55 chevy prostreet
 
#4 ·
You got 2 junk carbs...At idle (primaries near closed) your carb should run only on the idle circuit...If you screw'd in the idle adjust screws and your motor ran, its gitt'n gas from somewhere else.A bad rebuild mistake most likely...A good rebuilt Qjet isn't easy to find...Holley and Edelbrock do a good job, and you pay for it...If your original carb was junk, then get a good core at a salvage yard. Either way rebuild it yourself. Low cost, good results.

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68 El Camino...Slow, Much Work Required
98 Z28...Fast, No Work Required
Goodfellow AFB, San Angelo, TX -- Where? That's what I said..
 
#5 ·
Don't be offended, but you didn't have the idle adjust turned in far enough to bring in the primary circuit instead of the idle circuit did you? No matter what jets/rods the carb has, you should still be able to stall the engine with the mixture adjustment screws turned all the way in if the butterflies are closed, and there is no other vacuum leak on the carb.

[This message has been edited by Blazer1970 (edited 12-15-99).]
 
#7 ·
Hey guys, thanks a lot for all the responses. I come to the conclusion the carb is a bad rebuild. There is definitely fuel leaking from somewhere else. I got it running lean as possible but still has tendency to flood. I going to rebuild the old carb while driving around with the '74 then replaced it and if all runs well go ahead and take back the bad rebuild. I sure glad I paid the core charge and kept my old carb. Thanks again for all the suggestions.
 
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