General Category > Quadrajet Carb Talk and Tips

Very rich at idle

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Mla1:
Attached are pictures of the sizes of air bleeds and jets.  Metering rods are stamped 44. Hole size under the mixture screws are #44.  Idle air tube holes are smaller then a #60 drill bit. Due to no numbered bits smaller then #60 i cannot get that exact size.
Additionally the engine is a all stock 396.

Cliff Ruggles:
You are only measuring the top of the idle tubes, the restriction is on the bottom of the tube.

I don't see measurements for upper or lower Idle Air Bleeds?

You only measured the upper MAB, what size are the lowers?


Do me a small favor, provide the fractional size not the bit number I don't have a size chart anywhere near my computer......

Kenth:
Looks like you have a "frankencarb".

1965 to at least 1967 Chevy BB Q-jets uses upper idle air bleeds in the airhorn, next to the main circuit air bleeds, sized about .040".

Your carb has an airhorn from a 1971 or later Chevy/Truck Q-jet, and these carbs uses upper idle air bleeds in the float bowl, next to the idle down channels. For CBB´s usually sized about .069".

This would mean that your carb has NO upper idle air bleeds at all, and that would make a crazy rich F/A idle/lowspeed mixture.

HTH

Cliff Ruggles:
Lacking upper idle airbleeds will also cause the float bowl to drain into the engine after shut-down.......

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