My 65 coupe w/holley 1850-2 600 CFM carb is stalling out when I put it into gear and only runs for a short while at idle before giving out as well. Plenty of fuel is getting to it and I have the floats properly adjusted. The only way to keep it running is to pump the gas which makes me think the main jetting is cloged somewhere. any ideas/suggestions?

 

Update: I took the carb off and used an air compressior and carb cleaner to clean it all out really well. I put it back on and it seemed to run really well at idle, I took it down the road and about 30 sec later it started stuttering and stalled out again.

 

I'd be looking for a vacuum leak or clogged primary.