Classic/Antique Car Repair: 1960 pontiac 389 catalina, valve action, valve train

Question
I have a 389 catalina that started tapping and backfiring through the carb. any sugestions

Answer
Sounds like it could be something in the valve train like a broken rocker or bent push rod on an exhaust valve that is letting trapped exhaust gas spit out the intake valve on that cylinder when it opens. Or it could be a bent intake valve. I would first take a compression test on the engine and see if here is one low cylinder. Then remove that valve cover and do a visual check of the valve action on that cylinder. If the visual is ok and there is a cylinder with low compression then it is time to take off the head. Now, did this start all of a sudden? let me know.