I have JB Weld on a motor case that has a small crack .
I wire brushed the area and finished it with a good dose of brake cleaner .
Pressed the JB into the crack as much as possible and left a layer around and over the crack about 3/32nds thick .
That was 5 or 6 years ago . Many hours and lots of heat cycles on that motor .
The JB is still in fine condition , just a touch darker . ;)