I know it's aways better to just do something right the first time, but I can't think of any better way than F'ing something up royally to really learn a lesson. Often these lessons come when you're completely ignorant to the fact that you did something wrong. Let's hear some stories, I'll start. Yesterday I found out that a GM starter bolt is different than a regular 3/8-16 bolt. I'd never really looked at one before aside from acknowledging what it's length and thread was. I'd installed the starter on my SBC with 1 real starter bolt, and one generic 3/8 bolt. After a few months of no issues, I went out to start it the other morning, and got a horrific grinding noise. I looked under the truck and found half of the starter's snout on the ground. Turns out, the starter pivoted slightly with the narrower bolt and had cocked itself at a slight angle to the flywheel. The result? It jammed the starter gear in the flexplate and busted off the end of the starter. Price of that lesson? $50 for a new starter and correct bolt and 30 minutes of time.