If we go for stupidest.....I had just rebuilt a 390 in a Cyclone GT and dropped it back in. Dist was out so I could prime the oil pump. Put dist back in, crank crank crank, gas gas gas, no bang. D'oh, 180 out, didn't turn key off, just lifted the dist up.

Old timers....you know what happened next.

As I pulled the dist out, the shaft turned a little, points did their thing and the now free distributor arced to ground setting off a crankcase explosion. Lost eyebrows, hearing for a few hours, distributor in ceiling of garage of rented house.

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Eric, CPO, Submarines, retired.
Here's a sig line...
Mine: '68 Corvette LS1/4L65E, 83 240D, 2000 GMC 4x4, 08 FLSTC Anniv
Hers: '72 Corvette 454/4spd, '99 MB SLK, '93 Metro vert, 78 240D, '92 Silverado, '65 Fjord Rustang, '59 Fjord Fairlane, '17 Slingshot.