Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

APT adjustment screw adjust to smaller or larger jet sizes

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GSP7:
If I have to adjust my APT many, many turns up, like 5-6-7 etc etc turns , to try and get rid of hesitation/"boog" ... Does it need a bigger primary jet ?

In other words: Will a  larger jet size need less APT screw turns up than a smaller jet size?

My original 17080513 carb(1981 chevy K20 truck)APT was set at 2 3/4 turns up. Ran perfect

My new rebuilt 17080213 carb with the same size primary jets and rods installed as the above carb is requiring alot more APT turns up, am still  trying to get rid of a slite hesitation/ Boog off idle throttle acceleration.

I would think the APT adjustment would be about the same as the original carb

. 8)

GSP7:
???

GSP7:
Checking in for any answer after 90 views

 ???

Frank400:
well, the apt controls the light load cruise mode.  So if you're lean in that area and turning the apt screw counterclockwise still does not work (I am assuming a later carb with the apt screw accessible from the air horn), then you have to go to a smaller metering rod.

Kenth:
The answer to your question is, yes.

And, even if the same jetting there is often different idle/lowspeed calibration between Calif. and other units especially if one is Rochester made and the other Carter made with the same application number on it.

The "tip-in" test will tell you what the engine needs.

HTH

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