Years ago I JB'd 2 chevy 1.5" exhaust valves together as a demo for the stuff, it sat on the counter for years with guys trying to break them apart by hand. One day i got tired of looking at them and put it in the press. The valve stem broke before the JB let go.
I also used it to repair a 50cent piece sized hole punched in the bottom of the engine case on a dirt bike, flipped the bike over, cleaned and scuffed around the hole, JB'd a beer can over the hole with a couple more layers on top,next morning I flipped it back over, filled it with oil and went riding, it held for close to 15 years of riding "after a skid plate was installed" before it started leaking.