[nathanmargolis]

Not an ASE mechanic but it could be all things mentioned with not being distributor 180 out because the car was running fine.
Does the Cobra run? If so, start it, heat it up, and then touch each header tube right off the head to locate a possible dead-weak cylinder. A few drops of water a sizzle will tell you if the hole is running. That way you can isolate the cylinder if there is a problem.
To me a pop through the carb could be a bent pushrod and easy identified by pulling the valve covers. Worse case scenario is a flat cam lobe.
Most times you can see a flat came lobe by lack of movement in rocker arms.
Probably just a simple tune-up problem though and somehow I bet it could be a bent exhaust pushrod. Good luck in your diagnostics.