I have the black exhaust sealant crap that you use on slip fits.  Ive had good luck with it in the past not leaking.  Same stuff we used in the shop to reseal stuff up with.  VERY tacky and nasty, and dries in a weird semi solid state once heated with the exhaust.  Its basically like tar, but opposite.  Its liquidy when cold, and dries semi hard after being heated.

I just heat them up with the torch and they come right undone.  The way my system was built was the reducer with 3 bolt flange welded to the bent pipe, slip fit into a Flowmaster with clamp, slip fit out of the Flowmaster with clamp, and then all welded pipe from there back.  When I took it all apart, I just heated up the Flowmaster to take out those crimps, then I spun the pipe in it with channel locks until it was loose, and it slid right out.

 

It was the actual flair of the reducer that meets the header.  It was the last 1/8" or so around the entire circumference of the reducer that cracked.  Its basically the point where the triangle clamp ring makes contact with the flair in the reducer.  The clamp ring scored the pipe I assume, because it cracked right along that contact point.  The metal of the flair is rather thin at that point.  Im using the stock hangers with new rubber isolators, and the exhaust is aligned very well.  So well in fact that even with it broken, it hung aligned well enough a good 90% of the exhaust was still going through the system, and I didnt notice it was even broken until I tried to take it apart.

 

As I said, when I first built it I was very careful to make it line up right as not to stress anything.  Hence why I had the one piece custom bent instead of just "making it fit".  I also reused the stock hangers.  With the exhaust just hanging in the hangers and slip fitted together without clamps or anything, the pipe lines up damn near perfectly with the outlet of the header.

 

Im not too worried about this since I managed to find my second unplated reducer, as well as a store that sells unplated ones.

Im still up in the air if I want to try and just clamp it.  I figure, if it gives me problems, the worst that can happen is I end up welding it.  But, if it works clamped and the thing fails again at the same point, I will be able to replace just that one piece.

~T.J.