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Old 06-13-2005, 08:08 PM
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QudraJet Adjustment

We have a 350 SBC with a Quadrajet four barrel that is running rich. Tried to adjust idle screws but they are at base of housing and are odd shape, almost eliptical. Cannot find any screw driver or tool to fit into opening and on the adjustment screw. Any suggestions? ? THANKS. . . THERESA

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Old 06-13-2005, 08:41 PM
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I inherited a Q-Jet adjustment tool made by K-D that has an interchangeable end for what I think you're talking about. I believe NAPA sells them. You might want to check there.
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Old 06-13-2005, 09:26 PM
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Also on Q-jets, the upper air bleeds can get plugged and cause them to run rich.
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Old 06-13-2005, 10:48 PM
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They are pretty easy to get at, that is, if the factory sealant is removed. If you still have the factory sealant, I would leave the idle mixture screws alone and start looking elsewhere if it is indeed running rich. I once had a problem with the power piston not operating smoothly, causing the car to be un-drivable. Cleaning that out cleared that up right away.

If you do in fact need to adjust the idle mixture scews, www.chevyhiperformance.com did an excellent article on the proper procedure. I haven't tried it, but I also haven't needed to.
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Old 06-13-2005, 11:43 PM
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The later model Qjets have whats called a "double D" head on the screw. They are usually behind a metal plug that is pressed into the base plate once set at the factory when new. If you can now see the screw head, someone has already removed the caps and adjusted the mixture screws. Those carbs are inherantly lean no matter how far the mix screws our turned out. You may want to check the float and its setting. Some times the floats begin to sink and the fuel level raises and ends up dripping out the primary nozzles. This can be seen when the engine is idling and then look down the carb. If you see fuel dripping from the primary nozzles, its time for a rebuild and float replacement.

Here is pic of the carb tool. You can also take a piece of 3/16" brass hobby tubing and slowly pinch the end closed until it fits the screw.

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Old 06-13-2005, 11:58 PM
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Sometimes a short piece of vacuum tubing can be forced over the head of the screw & used to turn it.
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