Concerning the JB Weld Epoxy the slow curing one takes a higher temp then the fast curing JB Weld. I also think the slow curing one is stronger but have no proof.
Duro is another company that is still around used to make Epoxy in that has the same temp range as the slow curing JB Weld.
If you think you are going to have a temperature issue be sure to read the label.

With the fast curing JB Weld you could make an on the road repair on your vacuum line if nipple broke off as long as you are careful to reinforce it with enough epoxy.

I have used brand X type cheap epoxy and it sometimes won't even take the heat in the interior of a car on a hot day.

__________________
84 300D, 82 Volvo 244Gl Diesel