Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Dieseling
quadrajam:
My point with the distributor was that I was willing to to try anything at that point.
The distributor had nothing to do with it.
Sounds like your on the right track.
QJ
68rs/ss:
Watching this tread with interest as I am having the same issue. Nervous to increase by-pass air any more to the point where I went too big. At .116" already. How large should one go before looking elsewhere in idle calibration? Such as in the idle air bleeds or idle tube restriction size?
Kenth:
7040203 and 7045213 has the same specs, .092" upper idle air bleeds, .063" lower idle airbleeds, .039" idle tubes and .051" idle down channels.
I would start with this recipe for your carb on your engine.
Chevynation:
--- Quote from: Kenth on October 17, 2023, 12:47:46 PM ---7040203 and 7045213 has the same specs, .092" upper idle air bleeds, .063" lower idle airbleeds, .039" idle tubes and .051" idle down channels.
I would start with this recipe for your carb on your engine.
--- End quote ---
Thanks Kenth. I’ll be sure to check the idle bypass air hole size when I take the carb off tomorrow. The carb is great everywhere else and Cliff really was spot on with the recipe he put in so I don’t want to mess with it. I’ll just spec it out and do one change at a time. Idle bypass air increase by .010 should hopefully cure it depending on the current size. I’ll keep you posted tomorrow. Thanks.
Chevynation:
.063 Idle fuel tubes and 0.196 idle bypass air. Took the carb off without touching the curb idle screw and the transition slot didn’t look bad. It must have been getting too much air because that slot exposure is with the idle screw backed all the way out. Im not too familiar with quadrajet but should there be transfer slot exposure with the throttle blades closed? I know holleys you can close the blades and have zero exposure. I shaved some of the gasket off to fix the manifold port on the carb because it was just blocking the hole. I was shocked to see how big the bypass holes in the base plate were. Correct me if I’m wrong but I traced the idle bypass holes from the main body down to these two holes on the baseplate and they’re a good size. I went to touch the secondary air flap and the tension spring broke. Good thing it broke now instead of on the car. Pretty weird but no big deal. I’m thinking that I go down .010 instead of up on idle bypass air but I would like an answer regarding the slot exposure with the blades shut. Any opinions?
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