I threw away 2 of those POS carbs for the same reason. That plus vapor locking issues due to the carb being made from the wrong material to sit on top of a hot V8 engine.
The problem is the accelerator pump seal is getting stuck the the pump cylinder bore, which cause the whole carb to have a sticking point right after idle. The cylinder bore gets a groove in it which captures the pump seal.
My advice is to throw the carb in the trash, tell everyone you can that these carbs are junk, and get a holley 3310.
Edelbrock makes really good intakes but should be ashamed of themselves for making a carb like that.