Friend of mine had a POS 76 El Camino with a 305. I decided to mess with him one day and pulled his distributor cap off and run a #2 pencil around about a dozen times inside the cap and then put it back on. When he went to fire it, it popped and back fired and run like shet cuz the spark jumped around on the lead inside the cap. It only took him a few hrs to find it. I expected it to take much longer, and I'm not sure I'd have told him after 3 days. Punk owed me money. It was worth the laugh.