What's the deal here?
Are the studs threaded their entire length or are they just pressed in there so tight they can't be moved?
How does one get them out?

I realize that if they're threaded, you'd have to loosen the nut, then put another nut ontop of it as a locker, then turn it clockwise..as far as it will go, but how do you do this when thestud snaps off immeadiately?
Even ifaguy WAS able to do this without snappin ing the stud, they'd eventually have to use a pair of pliers on the other end, becausehe'd run out of room for the nuts and there's nothing on the other end.

Also...any tips on getting theTOP nut andstudout ofthe flanges between the cat and the manifold?

Why couldn't they just use good ol' nuts and bolts?!?!

 

They are threaded all the way. If you snap one off flush, you'll need to drill it and use an easy out. If you are trying to remove them, then I recommend you have heat available. Heat the nut and carefully remove it. Repeat on the rest of the nuts. If you really need to remove the studs, then heat the area near the stud and then remove it.

If things are still being stubborn after heating them, you may need to 'shock' them by rapidly cooling the area down.

If you are trying to get the studs out of the cylinder head, then you shouldn't use heat on the head, but you can use it on the nut.

And to answer your question about nuts & bolts... Well, main reason typically is that on the exhaust manifold to y-pipe connection, the flanges on the manifold cannot be made flat enough in the area where the bolts/nuts would rest without weakening the flange. Threads in a cast iron flange are stronger than just a thru hole.

 

Thanx swartlkk

Two follow ups though.

The first. Is there any reason I can't just drill through and removewhatever's left of the stud, then use some good stainless nuts and bolts? You mentioned reasons why they go with threads all the way. I already drilled out one hole in the muffler flange. I still can't seem to get what's left of that stud out. What's left is about 1/16" at it's thickest point and is only about 160 degrees around.

I don't have an easy out. I think my neighbor has one. Even if I heat and cool them, I can't see that working. If I can't get the local pipe guy to do it by the weekend, I'll give that a try on the rest of the holes....and heat on what's left of the one I drilled out.

Second, (if I DO try it again)...Do you have any suggestions on reaching that top bolt on the cat manifold (y pipe) flange? I already hit the hell out of it with pb blaster (no heat though) and I think all I've accomplished is rounding the nut off ! I had to use a 19/32 socket becauseI don't have a 15mm socket (I have 2 sets for some reason the both skip from 14mm to 16mm)and I couldn't get to it witha 15mm wrench. To compound matters, the 19/32 was a 12 point and slipped off pretty easily when trying to use the ratchet with a universal at the angle I was on.

Anyhow...I'll probably be taking it to the garage to get it done, but if you have any additional input, I'd be glad to hear it.

Thanx again.

 

For the rounded over nut you may need to try something like the Craftsman Damaged Bolt & Nut sockets if you have the room for them. I have this set and it has saved me from having to cut off the nut with a torch numerous times.

Even with a set of sockets like linked to above, you'll want to apply heat. With any frozen on hardware where heat is an option for removal, you can always thermally shock the materials. Heat the object with the internal thread, then rapidly cool it off with a non-flammable liquid. A few cycles and this will loosen the bond between the thread faces.

And no, there is no reason that you couldn't drill out the hole and replace the stud/nut with a bolt/nut. Stainless hardware really isn't necessary, especially when it comes with it's propensity to gall.

As always when using heat on a motor vehicle, make sure that proper precautions have been taken ensure that you do not damage other components on or near the piece being heated.