General Category > Quadrajet Carb Talk and Tips

What carb should I use?

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dlong70elcamino:
Your right 77 cruiser it does i meant it does not have the one in the bowl.Even the early 70s carbs I have,have the one in the plate. It,s weird that Cliff does not talk about adjusting the one in the plate in his book.

markedmondson:
Most (maybe all) Q-Jets with base plate APTs are plugged by the factory to prevent field adjustment.  When Cliff repaired by carb, I asked him to install an APT adjustment screw.  Now I can tune part throttle richness with the APT from the front of the base plate with a screwdriver (turning CW raises the seated (high vacuum) position of the primary metering rods).

Interestingly, Cliff at the time commented he gets very few requests for this modification.

Cliff Ruggles:
The baseplate located APT system was used on a lot of Olds, Chevy and Buick early units.  It is however difficult to get the screw in the baseplate freed up without snapping off the ears on it.

The factory use Loctite and it is very difficult to remove, and the screw is hardened to prevent drilling it out.  We use heat and penetrating oil and can get them out in most cases.  We replace it with an external screw with a spring on it so it holds the adjustment......Cliff

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