first off you need to check the timing, and tell us what the initial timing is, and what your total timing is
what engine is this? do you have a vacuum advance distrib?
how old is the engine?
there are many things that can cause a backfire through the carb, one of the main reasons is bad timing, but backfire through the carb can also be caused by a flat lobe on the cam
what kind of carb is this? after it backfired the first time, you need to check the power valve, you may have blown it and are dumping a ton of fuel in the engine which is why its backfiring even more now.
