Dumb things that you did.......because you didn't know any better.

I tossed a 65 273-4 short block into a field because it only had a spun rod bearing. I built a 68 318 out of everything off that 273 including the cam and it was faster? Yup. I also cracked the 4bbl intake (318 block had dowel pins, Doh!) so I replaced it with a Performer. Did the Performer save the build?
Had no brakes in my Honda AN600 car, found I had no brake fluid. I had to get out of that party and get home so I put water in there, pumped them up and it got me home. Spent the next day replacing the rear piston seals and flushing the system.