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On my GMC, I ve got a quadrajet carb, The truck runs real rich and get TERRIBLE gas mileage. I try to adjust the mixture screws and it doesnt make a difference. I think it might be foulin my plugs, because its starting to miss pretty bad. I messed with the timing and it doesnt help. It seems like it doesnt rev very quick either and doesnt like to have the 4 barrel kicked in. I dont know much on carbs and Ive heard bad things about these carbs. Any help would be cool. :wall:
 
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The bad thing about q jets is they have lots of internal passages and have alot of parts. They can be rebuilt fairly easy, but you need to soak them in a tank of solvent. I think q jets are good performaning carbs, that work well
 

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qjets work well for some people, but they have to be tuned just right. its not easy finding someone who knows how to tune them though. i would slap on an edel/carter and be done with it.
 

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the qjet is a good offroad carb due to its center float design but yes its tricky to tune...
if you wanted to stay with a qjet get one from jet or someone else who can tune it for your vehicle before shipping it to you...
the problem with running a carter or holley style would be you need to make sure you get a spread bore carb because otherwise you'd have to either buy and adapter or modify the intake or get a new intake...
the first 2 of which would probably not allow it to perform to its full potential...
a new intake wouldnt be so bad as long as you choose the right one for your cam and so forth...
if you have a welder you could also build your own adapter plate or make a custom high rise for the new carb...

as for the carb you have allready...
it may have a stuck float or something wrong with the needle valve...
those are the 2 most common rich running problems with those carbs...
 

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I have two answers cause it depends on if the thing has been on the truck and if the problem just started happening.

1 If the qjet has been on the truck rebuild it.


2. If the you just bought it, how big is the carb? on a stocker if you go above 650cfm your looking at no lowend power, you could try to jet it way smaller

or rebuild it(sounds familiar) :roll: ., then maybe check to get a jet kit, lower the jets one size at a time, also look at the spring and spring rates. If the truck bogs upon the secondaries opening maybe opening too early. heavier springs are one of the things you can change to get it just right.

getting a holley is not the answer in my book unless you like to tune carbs, they are like night and day when the weather changes, and if you know about east coast weather it can change in a hurry!

an edlebrock carb might be the ticket, they get phenomenal gas milage.
 

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Discussion Starter #6
The carb has been on the truck for a while, but it always seemed to over fuel in my opinion. It never had very good throttle response. It would basically just power out in a hole, In 4lo. Its a stock 350 with a edelbrock intake. I know it shouldnt be a pwerhouse, but damn at least it should pull its a$$ around. once you get the rpm up its not too bad, unless you want to you use the 4 barrel, then you might as well turn the switch off. It ran ok for a little while, but when we were running on top of that crx, I backed intot he car hard and it just went 6-7 cylinders. I checked the connections but they were ok. Stuck or defective float?
 

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Yup sounds like the floats, check both
 

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Most important is weather or not you have an electronic Q-jet if so you are screwed....early 80's to 86 ?

If not you are good to go. Try this link- http://www.florida4x4.com/tech/quadrajet/

If you are having off idle problems look hard at you accelerator pump the seals get hard and cause trouble. Start with a basic rebuild and go from there.

Good Luck, Todd
 

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The bad thing about q jets is they have lots of internal passages and have alot of parts. They can be rebuilt fairly easy, but you need to soak them in a tank of solvent. I think q jets are good performaning carbs, that work well
Absolutely,, when rebuilt and working properly Q-Jet makes one of the best "Daily Driver" road, truck carb , even some mild performance engines can benefit from its beautiful driveability
 
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