Quote:
Originally Posted by carbking
That carb appears from the pictures to have:
(2) idle mixture control screws
(1) idle air bleed screw (the one in the center)
(1) fast idle screw (the one on the linkage)
There is no curb idle screw. The screw on the linkage should only be used to control the fast idle (engine cold) RPM.
Without knowing exactly what carburetor you have:
Many of the Pontiac AFB's with no curb idle screw had suggested INITIALsettings (engine at operating temperature) as follows:
Idle mixture control screws at 1 turn (2 1/2 turns is the maximum) (with the RAIII cam, I would suggest 1 1/2 turns starting point)
Idle air bleed screw at 1 1/2 turns
From there, as Sirrotica posted above, it is trial and error
Something to try would be run the engine at a fast idle, maybe 2500 RPM, then manually close the choke butterfly. The engine should slow. Release the choke before the engine stalls. If there is crud in the idle circuit, this will sometimes clear it.
Jon
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That screw by the linkage isn't the fast idle screw (the fast idle screw is actually stripped out, but cold idle is a separate issue for another day). It is an idle adjustment that I believe someone added, as my GTO does not have this screw. I can't get the engine to idle (I probably should point out that it's a manual transmission) unless I turn this screw. If I back this screw out, I can't get it to idle using the mixture screws and the large middle one. I will try your suggestion using the choke. I tried Sirrotica's suggestion of bottoming out the mixture screws (and the big one). I realize that the suggested settings are a starting point. The engine was recently re-ringed, plugs, wires, etc. are new, point dwell is correct, timing is correct, so I really believe it's a carb issue. I just can't seem to get a decent idle.
Importsmasher