This is happening to the carb on my 85 El Camino. The carb is a quadrajet E4ME, thanks.

usually happens because the the timing is retarded, causing the throttle to jacked open to keep the idle speed up. Make sure the timing is set correctly with the vacuum advance disconnected if it has one or the timing control wire disconnected if it's computer controlled.

Also caused my needle and seat worn out or heavy float.