Quadrajet fixed Idle air bypass

Houtan

Member
Hi everyone,

Do we really need fixed Idle air bypass on Quadrajets? I tested two type of Quadrajets first my original 455 stage 1 Quadrajet ane secont I have a Quadrajet from 1968 Pontiac GTO. both of them on my 455 stage 1 when I tap close the fixed idle air bypass my Idle will goes better. do we really need them?

Cheers
 
The primary side of the Quadrajet is so efficient that it does not take much to initiate fuel flow from the primary nozzles. On some applications, you can get nozzle drip when the idle speed screw is turned in too much. The symptoms are always the same. Rich running and no response from the idle mixture screws. The reason, the engine is running on the mains instead of the idle system of the carburetor. Fixed idle bypass allows the throttle to be nearly closed while the engine is running at idle. It may help some with bigger cams. If your engine runs better without it, you are golden.
 
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