backfire problem

[8AV8]

I put my drivers side header back on last night after changing the gasket and when I started it the car backfired. Now its missing and backfiring. Wonder if I messed up a plug wire...suggestions, my car has never backfired and I'm more of a "parts installer" than mechanic.

 

[1970gsx]

Absolutely! The coil pack has numbers by each wire so make sure it goes to the correct cylinder. The cylinders from the front to the back are 1,3,5, on the drivers side.