Exhausted
Included in my “inherited” parts stash was a new exhaust (never used, but a tiny bit of rust). It included nearly everything I would need to replace the exhaust from the manifold on back, but I didn’t realize I had anything other than the major bits until after I bought a $50 exhaust hanger kit. Oh well, spare parts!
The old exhaust was still servicable, but very rusty. It was just going to be in the way when painting the frame, and I had this new one to replace it, so off with it!
The exhaust on my car consists of a downpipe, a stright(ish) pipe, and a muffler/tailpipe. The downpipe is supposed to attach to the manifold by three studs (mounted in the manifold), lockwashers, and brass nuts (lol).
Mine was held on by two rusty studs and nuts. The other stud was broken off and none of them had washers or brass nuts. On one the nut was so rusted that the stud twisted out when I tried to take it off. It would have been awesome if they all did this, but the other one was firmly embedded in the manifold, and the missing one was broken off below the surface.
If you are replacing the exhaust on your car and the existing studs look usable, you may not want to replace them as it is a giant pain in the ass. Then again, if they look usable they probably aren’t as rusted to the manifold as mine were.
I tried to use an extractor on the broken stud, but that ended up snapping off, as did the drill bit when I tried to start over. I finally ended up drilling out as much of the old stud as possible then using an air chisel with a pointed bit to break the remainder loose and fish it out. I ended up with a only a ¼ moon like piece. I didn’t have a tap and die set, so I somewhat rethreaded the hole by running a bolt of the same size in and out a few times.
Two down, one to go. The last stud was intact, but horribly rusty. I had been hitting it with PB blaster regularly for a week, tried heating it with a torch, tapping on it, and reasoning with it, all to no avail. This thing was not budging. Finally I just drilled it as close to the threads as I could then tried to twist it out. Most of it came out:
Everything but the threads anyway! More time with the air chisel and I had the rest out. The threads on the hole were a bit messed up though.
After some fiddling I got the new studs in (after giving them a coating of anti-seize). The best way to do this is to thread a couple steel nuts onto the end, lock them together by loosening the inner one while tightening the outer (forcing them into each other), and then using a wrench or socket on the outer nut to thread the other end of the stud into the manifold. The studs have a non-threaded section between the short manifold side and the longer exhaust side. I tightened them into the manifold all the way to this point, which brough the end just about flush with the other side of the manifold flange:
Here’s where I hit another snag. I could fit the downpipe in just fine, but I could not get the gap between it and the manifold to close. I’m surprised I didn’t strip one of the brass nuts trying. After a couple days of no progress I finally got out the calipers and did some measuring.
The new pipe extends 0.475″ past the edge of its flange:
The manifold has a slightly larger diameter (to accommodate this pipe) that recesses 0.35″ into the manifold:
Simple physics dictates that two objects can not occupy the same space at the same time (quantum physics, however, does not agree). That leaves me with a 0.125″ gap to fill between the flanges. The crusty old gasket I pulled off measured roughly 0.2″ thick. I think it may actually have been two or more gaskets stacked on each other:
The new gasket that came in my kit is 0.05″ thick:
My old exhaust pipe extended a bit less at 0.4″, but even then the new gasket wouldn’t compress. I measured the depth of the recess in a few places since it wasn’t uniform, then transferred these to the pipe extension, and cut off a thin ring.
I put the new gasket back in and re-secured it to the manifold. While it looked better, I could still feel a jet of exhaust leaking out. So I took it apart again, ground down the end a bit more with a dremel, and used the new gasket that I found in my big box of inherited parts. It was in a yellow envelope and I think it came from TRF. This gasket was easily twice as thick as the one I got from Moss:
his time when I bolted it back together the combination of shortened pipe and thicker gasket resulted in no noticeable leaks. There might be a little sneaking by, but nothing I could detect. It looks a lot better too:
I recommend that you fit the entire exhaust system before tightening the nuts and the clamps between the sections. If you have to play with the manifold side a bit, it is a lot easier to move the pipe around while the other end of it is supported by the middle pipe.
Speaking of the middle pipe, it took me a long time to figure out where the hanger bolted. I was so busy looking for a spot on the frame or the floor that I totally missed the obvious location on the transmission. The hanger has a nut welded to it that replaces the one on the transmission.
I think my old exhaust must have just been hanging here without support, because I don’t remember pulling anything off from this area. The exhaust passes through the “T-shirt” part of the frame, so it may have been resting on the lower portion of this. The old exhaust was also welded where the mid pipe met the downpipe, which I elected not to do.
The muffler attaches at two points - one by where the pipe comes in, and the other where the tailpipe leaves. I reversed the hanger-to-frame bolt in the front mount because it was easier to fit a nut in the space between it and the trunk than to finagle the bolt through there.
I also had to remove some other weird hanger that ended with a very wide metal hook (think of a taco bolted to the strap). I have no idea how it could have attached to the old muffler, so I wonder if it was even used. The hanger by the tailpipe is pretty straightforward.
Finally, here’s the mouse nest that was blown out of the muffler (which had spent some time stored in a barn) when I first tested the new pipes:
The mice are presently unaccounted for and may still be inside the muffler.