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[Rob Doe]

Vangogh, can ya paint us a little better picture of your situation? LOL Are you able to drive the car? Does the engine stumble and then smooth out at higher rpms? Does the GAV adjustment recommended above make a difference?

IMHO, your description describes a lean condition when transitioning from idle rpms to low speed rpms. This could be an air leak at the carb to manifold, manifold to block, or a leak at the vacuum port for the wipers??? Between carb halves???

The transition from idle to low speeds is a naturally lean area on the Zeniths. The compensating well, (the hole that the idle jet protrudes down into) serves a dual purpose. It provides fuel to the idle circuit, and when the throttle is opened to go faster, it provides an extra shot of fuel very quickly to prevent the stumble that you describe. The fuel supply / level of the compensating well is controlled mostly by the compensating jet, and partially from the GAV circuit.

If there are no air leaks, I'd expect a problem somewhere between the float bowl and the tip of the cap jet.