First off, are you getting power to the battery wire on the cap? I had a problem similar to this, I turned a corner and my truck backfired really loud out of the exhaust then would.backfire through the carb because the rotor wasbt turning. Pull the cap off and put a long flat heas screw driver in the rectangular hole in the rotor and bump the key. You should be able to see the screw driver move. If it does, the problem is electric, either the ignition coil, pick up coil, ignition control module, or condensor. If it doesnt, first thing to check is the distributor gear pull your distributor out and make sure the gear is in proper condition, no missing or ground down teeth. If the dizzy and cam gear are both okay, then your timing chain broke. Luckily it was just my distributor gear and not my cam gear or timing chain. Good luck. Report back with findings!