i dunno about jb weld in that kinda situation. it may hold for a little while it may not. heat and pressure to crazy stuff. did you flare the inside of the pipe to meet the inside of the hat for some kind of mechanical lock?
The outside of the 2 1/2" pipe i flared out slightly, and bent the edges of the cap hole in - once it was in the cap, it will not pull back out. Also, I used this stuff to hold a spoiler on a car where the bolt mounts broke off. It never moved for three years and there were no bolts in it.
I am just hoping for the best, and it is also a really tight lock, and also applied to the back, and in between. I just used this stuff most recently to make a column shifter on a 1947 Cadillac steering column only shift 3 times instead of 4 by making less grooves in the cam lock, so that piece gets smacked around consistently and it has held up like a dream. It's in a boat.
I personally think that if clamps on vinyl tubing with flares hold boost, this will. But I may be wrong and it comes apart, at which case I either try again (with $25 worth of parts) or get a spectre.