Hi i am looking at buying a 73 Chevy 4x4 has nice rebuilt 383 stroker motor. It has a Holley 670 Truck avenger carb on it fires up runs great then i go for the test drive i put it in gear and take off slowly and then i go to stab the throttle and it just falls on the face so if i lift my foot out of it goes back to running normal. It will drive if i barley give it any throttle but like i said so as i try to give it more it just doesn't want to go. I was thinking accelerator pump ? I have to be sure cause the truck is about 1.5 hour drive away. Thanks

 

Could be tuning. Could be any number of things. Could be a vacuum leak, bad gasket, low fuel pressure, bad float level, stuck needle valve, clogged fuel filter, dirt in carb, disconnected vac line, etc.

Did it ever run correctly with that carb or is this a fresh build?

 

sounds like too much fuel. check basics like fuel pressure, float levels etc...