Holley 1920 Help needed

The bowl vent is usually open at idle and closes when you open the throttle. The real issue is that the float may be set too high. Either there is junk in the needle and seat or the float level is set too high. Pull the bowl off and invert the bowl. The seam in the float should be parallel with the bottom or top edge of the bowl. If not bend the float lever to adjust. If it is level then pull the float out and look for a dad needle and seat valve. And see if there's any junk, like rust or sediment floating around in the fuel bowl. You DID put a new fuel filter on the car before running that new carb, yes?

Guys, there's nothing wrong with a 1920 carb - thousands of motors have left the factory with them.