I have my new Stillen exhaust and most of it is there already. The last piece I need to put in is the y-pipe that connects to the cats. That's where I've run into my issue. So far, every bolt on the exhaust has snapped off. That's ok, because Stillen gave me new hardware to use. While checking out how things will fit together I noticed that the bolts are welded onto the cat's flanges. At least, I think they are. I don't see a visible weld, but no matter what I try, the bolts don't come out. Right now, I have the factory y-pipe held to the new whatever-that-next-piece-is with a couple of C-clamps. I know that's not right, but I don't want to break the bolts off of the cats and not be able to finish up.

How do you normally deal with the cat bolts when installing a new cat-back exhaust? Do they come off somehow? Do you grind them flush then drill them out so you can fit the new bolts in there? Is there something else that I'm too dumb to think of? Should I just take it to a mechanic and and pay him to fix my screw up?

The car is a 2008 G37 with the 4 wheel active steering thing.

 

Why don't you just reuse those bolts and nut to attach the new exhaust? If the bolt you're talking about has a round 'bump' on the backside of it, it is not supposed to be removed.

 

I'd love to. The only problem with reusing them is that every other bolt has broken off between the flanges. That leads me to believe that the last four will do the same.

I believe my car's previous owner was from up north where they salt the roads. The bolting is badly corroded. In fact, I almost couldn't get the rotors off to replace the brakes. Every bolt that could get road salt is severely corroded.

 

When I did mine, only the nuts came off the stock Y pipe at the cats. The car was new enough that no liquid wrench or similar was needed.

Upon reassembly, that was actually the first piece to get installed because of the permanently mounted hardware at the cat flange.

Edit... heat is your friend. A torch might be needed.

 

Ouch I hope you were able to replace all those brake bolts along the way. As far as the exhaust, this might be the time to look at a HFC or Test Pipe. Those have open flange designs and would eliminate those corroding cats.

 

We ended up using a torch to heat the nuts/bolts when we changed the exhaust.

 

I thought about getting a high flow cat, but I've heard they make the exhaust kinda raspy. I absolutely hate that nasty fart can sounding exhaust.
Test pipes? Don't those basically swap the cat out for a straight piece of pipe? Aren't the cats there for a reason? Something about significant emission reduction if I'm not mistaken. I'd think that if high flow cats would make things raspy, no cats would be even worse, right?

Are the bolts on the headers actual bolts, or are they like the rest of the system and molded in as part of the flanges? If they're molded, I would suspect replacing the cats would just move the problem back one level.

 

I called my local Nissan parts service asking them if they sell nuts and bolts for my G37 x coupe exhaust. The guy said the bolt are welded to the flange. So I called my local infiniti parts for second opinion and the guy said they do not sell just nuts and bolts alone, but he check the bolt and said it can be removed, but need a bit of hammering. I do not know who is telling the truth? Pls. PM me if it is removable. Thanks!