Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

continual backfire out exhaust when at idle

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wiguy:
Rebuilt the carb over the winter using recipe #1 for my mild 350.  I have been told the popping out the exhaust at idle was caused by a lean condition.  I opened up the idle tubes, have 76 jets with 44 rods.  The apt screw was bottomed out when I rebuilt it, since then I've backed it out about a turn and a half, idle screws are out 5 turns and the the problem still persists.  After running at WOT it will idle and accelerate from a stop with out the popping.  I checked the timing and it's spot on.  Any ideas would be welcome.

Cliff Ruggles:
What is the carburetor number, and engine specs?.....Cliff

wiguy:
carb # 17059203  79 corvette L-48 motor. PO had it rebuilt and over bored, but original heads mild cam, headers, true dual exhaust, no cat, no egr

Cliff Ruggles:
Still using the large main airbleeds?

Might need more idle fuel (larger idle tubes/down channel), and raise the APT up to 3-4 turns.

Where is the float set at, and do you have one of our kits installed?.......Cliff

wiguy:
Carb was rebuilt using one of your kits, including new throttle shaft bushings.  It has the large primary bleed.  The popping is worse than before I rebuilt it which is why I'm wondering if the problem was too rich rather than too lean.  I'll raise the APT and see what that does.  Thanks

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