Catalytic converter to muffler studs
 

I started removing my muffler as part of changing my differential bushings and had trouble with one of the nuts connecting the muffler to the cat. The PO had a cheap replacement muffler installed right before selling the car and it appears that the muffler shop cross threaded the nut.

Looking through the forum, there is lots of good information about exhaust studs for the manifold but couldn't find anything about catalytic converter studs.

Has anyone had to replace studs on the cat before? Any advice?

I haven't looked too far into it. Those studs get a LOT of abuse, even if you can get the old stud out, you may not be able to thread in a new one.

May be better to cut the stud off flush, drill out what remains and use a bolt/nut on that flange. 99% of aftermarket exhausts use bolts/nuts and it makes re-assembly MUCH easier.

BTW I dig the user name!

Dale

if you were lucky enough to have a cat that was replaced, they have a bolt tack welded on instead of a threaded in stud. the bolt is FSN5-20-WA5

if you're not lucky, you get to drill out the stud

Is it for sure a threaded-in stud? I’ve had some luck on other cars with pressed-in exhaust flange studs. I cut them off about a half inch long so they don’t bend. Heat the flange up a little and just use a 2 lb ball peen and smack them out the way they went in. Then just replace with a nut, lockwasher and bolt.

Thanks for the information. I couldn't really tell last weekend when I stopped what type of stud or insert it is. I will wire brush the back and see if I can tell what it is. But I am leaning towards drill out and bolt. Will make life easier in the future.

That is the thing about these cars, each simple job grows. Need to pull the cat to fix this and should go ahead and replace the cheap muffler while I am in there.

I think all those studs and appropriate nuts are available at Mazdatrix.

I think they are all M10x1.5

If the stud is not broken you likely can get it out with heat. I use a MAPP gas torch (yellow bernz o matic), and while its not as hot as oxy/acetylene, its sufficient to get out rust exhaust fasteners.

When you put it back together, use copper or nickle antisieze so you can service it in the future..

Just looked at a friend's main cat yesterday, I believe the studs are M12.

You could probably replace with studs from McMaster-Carr.

Dale

same as the wheel studs, have seen lugnuts holding the cat on before

^^^^^^^^^^^^^
These guys are exactly right

In my minds eye I was thinking downpipe when clearly you were talking muffler

M12 for sure

Thanks for looking Dale. I will get after it in a couple weeks and report back.

Thinking to pickup a Tanabe medalion muffler while I have it apart. The PO gave me some receipts that included one for a $89.99 muffler and install.

The Tanabe Medallion is a good way to go. If you have some muffler shop special that needs to go for sure.

Dale