OK so today i'm trying to fire over the 454 and all it'll do is cranks and sputter a little bit, then it'll backfire through the carb. I'm really stuck on this one any suggestions on that it could be? i chacked and re aligned the distributor twice, checked the plug wires multiple times, loosened the rockers thinking that they may have been to tight and allowing the backfiring. i'm just really stuck and super frustrated. thanks a bunch.