This is my first time on this site. But from what I have read my questions can probably be awnsered. I have a 1972 f-250 with a 390 in it. I installed headers and rebuilt the carb, and now when I start it has a large vaccum leak noise coming from inside the carb. When I start it with the choke it will idle and the noise is a little quieter but it is still there. But when I turn the choke off it backfires when i try to keep it going and if I take my foot off the pedal it dies. Any help would be very grateful, thanks

 

Welcome sledhed, nice to have you on board and congrats, the 1972 F250/390 is a sweet ride and one of my favorite trucks.
Drop into the 1967 - 1972 F-100 And Larger F-Series Trucks forum: https://www.ford-trucks.com/forums/forum39/
Be sure to vivst your Alaska Chapter: https://www.ford-trucks.com/forums/forum152/ soon.