The first motor I built for a customer was a early (pre 1962) 383 motor in a 1963 dart that he had installed and made the motor run before I met him. It had the early cast iron 3 speed tranny with the ball and trunnion rear U joint, I sold him a later1964 model 727 and crankshaft out of a 1964 361 motor and was changing the crankshaft to make the later tranny work in his car, he wanted to watch me and I let him, he smoked and had drop ashes into the motor several times: rant:
It was in Hesperia, CA in the winter when I was working on it at night after work in either late November or maybe early December in 1971, it was cold, in the low 40S F and he wanted to go inside my home and have a cup of coffee to warm up, I was done torquing with the first six rods when he started whining about going inside. When we came back out, he said we were done so he was going home, I screwed up and didn't retorque any of the rods after he left, let along finish torquing #7 and 8 rods
We started the motor up and it ran about four minutes before one of the rod nuts unwound and allow that rod to separate from the crank and hit the block cracking it
That was the last time I have allow anyone to watch me work on motors, tranny, rear ends or any other part of a car project other than at the tracks
That is the worst thing I can remember screwing up on car projects, motors and so on at this time