General Category > Quadrajet Carb Talk and Tips

Lean idle and Exhaust popping

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TylerG:
Hey Guys, thanks in advance for any info I can get on this. I'm finishing up my first SBC engine rebuild including my Quadrajet with a great performance kit from Cliff. I'm in the final stages of tuning the QJet now and am a little stumped on getting my idle right. I'm getting a lot of obnoxious popping out the exhaust when I let off the gas, under load unless I turn the idle mixture screws out 5 turns. This seems excessive based on stock specs but understand I should be drilling the idle mix holes out and possibly the pick up tubes and down channels to richen the idle circuit to better match my build. When the truck is idling the exhaust is eye watering nasty. The idle screw on the side of the carb is turned all the way out and I cant get the idle below 900RPM. Any pointers on getting my idle mix corrected would be greatly appreciated.

Engine Build: 350 small block honed 20 over, 64cc Edelbrock heads, stock iron intake, Summit 214/224 cam, long tube headers, Cliff's HP Qjet rebuild kit (not including idle circuit parts) can get jet/rod numbers if needed. Timing is set at 14 idle and 38 all in. I think i'm getting about 9.5:1 compression.

Thanks
Tyler

Cliff Ruggles:
What is the carburetor part number?

How is it set-up, idle tubes, DCR's, idle airbleeds, bypass air, etc?

TylerG:
Hey Cliff, the carb is a #7041208. From what I can tell its the factory carb for my 1971 350. The carb is unmollested, so the idle tubes, DCR's, idle air bleeds and bypass air are untouched. The only thing that has been done to the carb is the new O power piston spring, 76 jets, 43 primary rods, AX secondary rods and SR Kit that I got from you.

Thanks
T

77cruiser:
Possible vacuum leak, if you can't get the idle down.

TylerG:
Thanks Jim, i'll double check for vacuum leaks. I'm getting steady 16" of manifold vacuum, for what it's worth.

T

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