2GV carb flooding

[1970greenmachine]

I have a 1970 C20 with Rochester 2GV carb that is fllooding my motor out. It will start sometimes but when it does it won't rev up and just coughs and spits. I noticed fuel coming out all over the carb, let it evaporate and just cranked it a bit. Fuel first started coming out the butterfly shaft on both sides so I thought something is pouring gas all over them. A flashlight showed the venturi boosters dripping heavily down onto the throttle plates. They even did it when I just injected gas into the fuel line; that's with no cranking, so no pump pressure or engine vacuum to get fuel flowing normally. What is this probably caused by? Thanks