Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
APT adjustment screw adjust to smaller or larger jet sizes
GSP7:
Im at 5 turns up on my APT screw,,,,, seems like the boog off idle throttle position maybe gone,,, maybe... maybe not.. (I only drive the truck occasionally down the hill from my house )
Is 5 turns up on the APT unusually alot more than average adjustment???
That "tip in" procedure mentioned above didnt do anything when I first installed the carb and did some tuning
novadude:
I wouldn't worry about 5 turns. In my experience, 3 turns +/- 2 turns is in the range if the jets and metering rods are right. If the tip-in test does nothing, it may be rich. I wonder if your problem might be elsewhere? Does the accelerator pump give a shot of fuel with a small amount of throttle movement?
GSP7:
--- Quote from: novadude on September 23, 2025, 05:21:39 AM ---I wouldn't worry about 5 turns. In my experience, 3 turns +/- 2 turns is in the range if the jets and metering rods are right. If the tip-in test does nothing, it may be rich. I wonder if your problem might be elsewhere? Does the accelerator pump give a shot of fuel with a small amount of throttle movement?
--- End quote ---
Im now at 5 - 4 1/2 turns and seems like the bog is gone. I only drive the truck once in awhile and have to go down a hill 2 1/2 miles leaving my house to test on flat road or back up the hill
I had cranked the APT all the way up to 7 to get rid of the bog then back it down bit by bit and test drove. over many days.... was down to 3 1/2 and thought the bog was gone, nope. Now im at 4 1/2 from 5 . I'll do several more test drive to see if the bog/hesitation is stiil gone or not
.
lightning boy:
IF it runs well at 5 turns that's not too much.
quadrajam:
Power piston spring could be weak.Get a new spring and put the 73 jet back.
I assume you've double checked the acc pump function and proper hanger arm
geometry as previously posted....??
QJ
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