list your most moronic thing you've seen done to a car

I bought a 72 New Yorker, only intending to harvest the drive line for my 52.
After getting it home I noticed it was smoking quite a bit.
The oil looked like it never been changed and just topped off. I commenced to do a change and MMO treatment. The new oil turned black immediately, man that engine was filthy.
With breather off I noticed the carb looked to have caught fire at one point. Oh well I planned on a total rebuild anyhow.
Fast forward many years in a moment of boredom, I decided to try and remove the warped choke plate from that carb to straighten, reassemble, and check the operation, etc.
What I never noticed was some PO had run a small screw in the choke tower to limit the opening travel of the choke! If I noticed that from the git, It may have been a perfectly good runner and not be fogging from the tailpipe.
My machinist, after tear down, told me he would of run it, after the fact, of course.. OH well, water under the bridge...