I have recently been tuning the carb to try and get my '66 with a 283 to run a little smoother. However, as I was adjusting it one evening I started it up and I had gas spewing out of the top of the carb. Figured it would be a good time to clean/rebuild the carb since the truck was sitting for 10 years. Everything was cleaned, new float, new fuel inlet needle and seat, new plunger, and lots or carb cleaner in every hole. So i put it back in, put a new fuel pump on ( it was leaking), started it up and it run superb for about 5 -10 seconds then coughed and shut off. When I went to start it up again I had fuel coming out the top hole again. The hole actually juts out into the circular air horn (I think that's what it is called). I am asuming the carb is flooding and the hole is some sort of release??