Man, Mizark347 your just having no luck with this new engine... WTF????? I remember when you coudn't get the thing to turn over.... at least you solved that problem. Just because smoke is coming out of the intake dosn't mean you blew a head gasket. Usually on a bad backfire a bit of smoke will rise, so don't worry about the smoke or your head gasket. Check thing's over again. Timing, Firing Order, Valve Adj., etc. etc. It's thing's like this that will cause a backfire on start up if not set proparly. (Especially if firing order is incorrect) If your fuel line is leaking really bad, it could cause your pressure to be down, either that or you got a fuel pump going on you or you just don't have your regulator set proparly. Take your time, go over everything (double check alway's) and fix your fuel press. problem, then try again.