Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Idle mixture changing.

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Cliff Ruggles:
Correct the high idle problem first.  I suspect you may be pulling some fuel off the boosters (nozzle drip) at that rpm.

To idle that high it's getting too much air from someplace, or too much timing at idle speed.

What is the engine combo?

What is the distributor doing and how is it set-up?....

CJK440:
Fixed the idle problem. When I pulled the carb to clean it thinking maybe dirt was causing the idle fluctuation I installed a new base gasket and didn't torque the front bolt enough. Now if I back the idle screw out all the way it drops to 500 rpm hot.

Is there an ideal primary plate position for idle? I know the rule of thumb with holleys was to have the transfer slot exposed as much as it is wide so the part of the slot uncovered looked square.

Any similar rule of thumb for the Qjet.

Cliff Ruggles:
Not really, but the throttle angle must be low enough so three things don't happen.

First you can't be uncovering any ported vacuum supply slots or holes.

Second, there can not be any fuel coming from the boosters (nozzle drip).

Last, the plates can't be so far closed that they are sticking in the bores.  It really helps to index and align the plates and install bronze bushings for the primary throttle shaft to help things out there as well......Cliff

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