I had just finished putting together a Gen 2 Hemi, first engine I'd built from a bare block by myself, and more money than I'd ever put into anything in my life. Everything had to be right the first time, as I couldn't afford to screw anything up. I got it in the car, put a little fuel in the carbs' throats, and tried to fire it up. It started... but was only running on two cylinders, like a shaking like a friggin Harley Davidson. Horrified, I shut it off, check things over, verify the distributor is in correct, and try again. Same result, over and over, until I foul out the plugs. Off I go to the parts store for a new set. Same results. Frustrated and discouraged, I quit for the day. The next day I have my brother look at it with a fresh set of eyes. He quickly points out that the spark plug wires are on the cap in the correct order... but reversed, so only two cylinders were firing in correct time.