I am trying to remove my muffler from the cat pipe at the flange and the nuts on there do not move and the studs do not have a hex head how do I remove it without cutting anything? 2000 Blazer 4dr 4wd LS trim

 

That flange should have nuts and bolts on it. You can try heating them with a torch or you might have to cut them out. I cut mine and replaced them with stainless bolts.

 

I was able to take mine off with a socket and a breaker bar. One of the studs broke but that was on the part I was replacing.

 

I use a small propane and oxygen torch to get the nuts glowing red. Haven't broken one bolt since going to this method. Previously broke about half of them and they are a real PITA to drill out. Must be hardened steel.