Idle circuit can't seem to run engine

[mother$hip89]

I can't idle the car under 1100 in park without the idle speed fluctuating, and to do this I have to move the fast idle screw until fuel drips from the primary Venturi. The mixture screws haven't really affected anything.  No part of the idle circuit is plugged. I haven't been able to find any more obvious answers like vacuum leaks (it even pulls about -18 at 1100 rpm).  Since it won't run until it's no longer drawing from the idle circuit alone, is it possible the idle circuit simply can't support the engine. Or is it possible jet sizing is at fault (even though it runs just fine at part throttle).

[77cruiser]

What was done to it? Did you have the idle tubes out?

[mother$hip89]

Other than a basic rebuild and metering rod change, it should be untouched

[carmantx]

You need to provide engine specifics.
Idle circuits can support idle but need to be calibrated correctly.

[mother$hip89]

1974 olds 350 rocket, unknown cam, but can't be too huge considering vacuum. The carb is 17057253.

[77cruiser]

Did you take the idle tubes out? They could be plugged, hard to tell without taking them out.

[mother$hip89]

No, I haven't. Only tested by blowing compressed air through. If I stuffed a small tube brush down the idle tube would it clean it or am I better off straight up taking them out. Also, is it unlikely then that the engine would need more than the idle circuit gives it when it's not blocked.

[mother$hip89]

I took out the idle tubes and cleaned everything out and that was it; I can undo the fast idle screw all the way now. Thanks.