Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Rich off idle stumble.

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77cruiser:
I'm getting a stumble off idle light throttle tip in. I have the linkage in the outer hole, was worse on the inner hole.
Combo 421 SBC Vic JR. 227/239 @ 0.05 hyd roller 9.8 CR 18 deg initial w/10 deg manifold vac.
Pretty sure the accel discharge hasn't been opened up, I didn't note it on my sheet.

Kenth:
18 deg initial is a lot and to me it indicates a too lean idle circuit.

What carb and recipe?

77cruiser:
17084226
Idle tube  .031
Idle down .052
Idle disc.  .093
IABP        .136
Idle AB moved to air horn .043
Lower idle bleed .062
MAB blocked drilled for Dual MAB .046
P jet   .074
P rod   52M
Inlet seat .144
Float 5/16
SAB .026
Hanger G
Rods   CV
Air valve 1.29

Goes rich at light tip in to about 10 AFR then back to 13-13.5

novadude:
Your idle calibration is similar to mine... I have .029" idle tubes, .043 UIAB in air horn, .062 LIAB, .046 IDCR.  Using .046" Dual MABs, and 74 jet w/ 54M rods.  Idle air bypass on mine is 0.089".   I have less cam (217/225 @ 0.050, 108 LSA).  I have 13 deg initial with ported vacuum advance (15 deg can).

I wonder if reducing the IDCR would help with the rich spike?

77cruiser:
When did you build that carb? How's it working out compared to the other one?
I took it apart & found one pull over tube on the sec. was off, brake booster fitting was loose. Nothing that would make it rich though, but I was able to turn the idle mixture screws in about a full turn & it's better. I might try putting a IDRC or put a bigger IAB in it.

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