Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Idle circuit screw response

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77cruiser:
Is emission testing required? If not you can up the timing & then you'll be able to close the throttle some.
Is the vacuum advance hooked to ported or manifold vacuum? Guessing it's supposed to be ported for emissions.

raf2330:
Yes on emissions. Have tried messing with timing as you stated. Have it to manifold normally. Put it on ported for test. Either way I've had this problem since going to the manifold and very mild cam (cam just to match Edelbrock 2.0 so it would still pull), just enough to mess me up on proper idle the last couple of years (doesn't get driven much at all) and be a pain for emissions, although we have made it pass, barely. I want to get it into the idle circuit at idle.

blazer74:
Better to go up gradually on the bypass air.
Time consuming yes.
Harder to go back smaller, you would need to bush and re drill
Or add screw in set screws from Cliff.
My guess would be .086 to start but I'm a novice.

raf2330:
Thanks again guys for the reply's. I have gone up gradually. It is responding some to the air screws now. Both shut will bring RPM's down, but not kill it. This is where I'm at.

Bypass air: .090 (stock was .050)
Idle Mixt. hole: .078 (stock was .050)
Upper air bleed in air horn: .110 (stock)
Lower air bleed: .060 (stock)
Idle tube: .050 (stock)
Idle down channel: .040 (stock)
Changed hot air choke to electric, plugged would be vac. leak.

So right now the screws are out 1 turn and my AFR meter/gauge says I'm a little rich, 13.5, so I feel like I need to open up the bypass air a little more. Definitely have more control, but feel like I need more air. Am I on the right track?

77cruiser:
Sounds like the right track. When you have the idle rpm where you want it, how much transfer slot is showing?

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