ok guys i need some advice. my truck started poping threw the carb the other day and i'm not sure why. i had headers on there but they had a crack so i found some ram horn and went to the exhaust shop. once i left there the truck was running good and quiet. in running around town i burnt out the heat riser in the passenger manifold. i parked it, and pulled the manifold. I taped and plugged the hole then put it all back together. When i started it up and went to pull out of the drive way it started to back fire on me. i drove around the block but it didn't get any better, so i parked it.
I was able to to play with it a little today and found out it was poping threw the carb. I reved it up, and it back fired then shut off. I have no tuning experence what so ever. This is my first V8 and i only have about 30 miles on it.
sorry for the long post but i know you guys like to have all the info.
It's a sb 350 target master crate motor, HEI( skip white), 1406 carb. nothing fancy just something to drive. i don't know where the timing is at a local hot rodder played with it and said it was good

it did run good untill now
What would cause this?????