If you put it on exhaust manifolds, it will just burn off right away, and even on cooling systems, if someone runs the car out of coolant completely and really overheats it to head cracking temperatures, the JBWeld will disappear, but by then you'll have a long list of other things to fix, too.

I wonder how many people who bought high mileage '69 220D cars or used transmissions in the last decade went out tonight to check for traces of JBWeld on their transmission output flange?