Popping in exhaust

Do I need to relive the nightmare one more time???LOL!!! We had a 72 Challenger 340 car, ran good but popped through the exhaust. Checked everything, wires, timing chain, ignition, no sign of problem. A couple hundred bucks later and more than that in hours the culprit was found...a cracked insulator on one of the plugs. They were new so we never changed them despite removing and replacing them a couple times searching for the problem!!! Just sayin'!!! Geof