Removing rusty exhaust bolts
 

Bought an M&K sport muffler and pre muffler for my 89 Carrera. Got the car on jack stands today and managed to get that plate off the bottom of the catalytic converter after lots of fiddling.

The bolts that connect the catalytic converter to the exhaust manifold look pretty bad and a couple look hard to reach.

Any advice on getting them off? If I were to cut them off, what's the best tool to use and which side of the bolt is best to cut? I sprayed them with penetrating oil before I called it a night.

All input appreciated.

Dont waste your time with penetrating oil. Just whip them off with a air gun or a big wrench and hope they snap. Bolts are cheap.

If that fails use a die cutting wheel. Worst case dremmel or angle grinder

Flame wrench if you've got one.

Cut them off
 

I just did this recently.
The best tool for me was a grinder.
It took about 5 minutes.

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Cutting wheel or torch.

some times just tighten them a bit more and they will snap ....

Just go with a Dremmel, cut the bolts off and be done with it.

If you get a grip on them just put your back into it, they will either loosen or snap. That is the easiest and most safe way.

Any ideas as to what to do after you Dremel/die grind the bolts heads and/or the nuts off and the shank of the bolt still will not come out of the through hole?

I have one completely out, two with the nuts broken off, two with the nuts Dremel'd away and then one with the nut and the bolt head mowed off and I still can't drive the shank out (used BFH). I don't have access to a torch.

I like oxyacetylene. Just burn them right out, and without the access issues of a grinder.

When you install your new muffler, use stainless bolts & silicon bronze nuts, and you won't have this problem ever again. I am lazy, cheap, and a blasphemer, so I used SAE 5/16 hardware - the local hardware store has the bolts, and 13mm tools work just fine on them. The nuts you will need to get online at one of the hardware vendors. Buy some extra, so if you bugger one of them up you won't have to pay shipping twice.

I understand these methods to get the head of the bolts off but then how do you get the shank of te bolt out of the casing

casing ? these should be straight through nut and bolts .. once one end is off you should be able to drive it through .. if you cant i would try cutting the other end off, failing that , i would undo everything else and just wiggle the whole thing off . it will come ..
dont get me wrong though exhaust work is miserable , and when working with jack stands can be exhausting .. ( wow that was bad )

Thanks for all the responses. I have a regular Dremel but cutting bolts with that is slow going. May run out this morning and pick up an angle grinder and some cutting wheels for it.

this is the perfect excuse to go buy an air compressor and cutter :)

Put a big bar and socket on the heads and pop them off, take a punch and hammer out the bolts. Our mufflers come with new nuts/bolts and gaskets.

While at the big box store, also pick up a good drill and some very good bits. I was lucky and did my exhaust on Black Friday and picked up the drill at a very good price.(my old drill wasnt up to the job and my compressor overheated when I used the air drill) I had to use a sawzall to remove the cat then a grinder and drill to remove the flange. Then a trip to Tractor Supply for hardware to install the new bypass pipe.

Air hammer for bolt shafts….
 

After I cut the bolt heads off I used the air hammer/chisel and knocked out the shaft
with the punch tool. You can use a regular hammer and chisel if you do not own a compressor and air tools.

If you use air hammer/chisel be careful as you can blow out the flange.
(ask me how I know)
Oh, and wear ear and eye protection with your head in the wheel well.
My ears are still ringing. (I am so lazy…..What ?…. Can't hear you …..)

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I did this job recently. Dremel, grinder, torch blah blah. $5 for PB blaster, better than WD40 IMHO. soaked all nuts, bolts several times over a couple days. ALL of my rusty bolts came right off. They were very crusty and all looked original. Just slap on a bypass pipe for a few additional horses and be done with it:)

OK. That was WAY harder than it should have been. Ran out and got an angle grinder this morning (how did I live without one all these years?). It took hours and involved:

The angle grinder and two cutting wheels
Dremel that died in the middle of the operation.
Propane torch
Sawzall
PB Blaster
Drill

The good news is the old exhaust is completely out now. The bolts were more frozen than expected and a few were ridiculously hard to get to.

The bad news is I nicked a rear shock with the cutting wheel and stuff started oozing out. So, tomorrow will try to find a pair of shocks (dealer maybe?) and throw them in and the new exhaust after work.

I think the toughest part is out of the way. I haven't been this dirty since I was a teenager, tearing apart my 73 Barracuda. neighbors were looking at me funny today.

Bolts….
 

You might want to use longer bolts than what M&K supplied to get the pre-muffler installed. It's just easier to get started if you use a bolt that is 1/4" longer.
I used these from pelican and they worked well. 8mm x 40mm
I also found it easier to mount the pre-muffler to the muffler and then mount everything together as one unit.

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