How do i cut out mufflers and replace with new ones?

[jperry1290]

My flowmasters rusted out on the bottom side and now have a few pin holes. Can I grind the welds off and remove? Or do I need to cut out and add sections of pipe?

 

[Broncobowsher]

How are they installed? Sounds like someone slipped the pipe into the muffler and welded in place instead of normal exhaust clamps.
What mufflers are you going to use? Exact same replaments or something that may be a different size?

It's hard to say exactly how to replace them. Being the muffler is rusted out, what shape is the pipe in? Where the pipe is slid into the muffler, that could be rusted out as well.

My plan of attack (guessing since I can't see what you are working on) would probably involve a sawzall cutting the nipple flush with the muffler body. Get the body out of the way and see if the pipe in the nipple can be saved. If so, how hard is it to grind/cut the weld. Maybe just cut the pipe, ad a little extension to one side and shift the muffler forward of back a couple inches. Just guessing as I am not sure what you are working with.

Now if there are clamps involved, things may be different. Most of the time the clamp is tight enough to dimple the pipe. Back to cutting the nipple off the rotted muffler and scrap the clamp. If the clamp does not come apart, take an angle grinder or cut off wheel and just cut it. Now cut the nipple lengthwise. This may work with a welded exhaust if the weld is just a tack weld.

Now if the new muffler is longer, just plan your cuts and cut it out.
If the new muffler is shorter, you will be adding pipe unless it was built too long to begin with.
If the offsets don't line up, and you don't have enough wiggle room to line them up, getting new bits of pipe to line things up.

Lots of possible routes, all based on unknown variables.

 

[Slowleak]

Lots of variables there. Welded, dimpled, or rusted pipes are a pain. I usually cut the pipe just forward of the clamp or weld. Then I slide pipe reducer over the pipe and into the new muffler and clamp it down. It's easy and gives you some extra adjustment in case the new muffler is a different length. http://shop.advanceautoparts.com/p/walker-hardware-reducer-41946/89026065-P

 

[Steve83]

Clamping is not trail-friendly. Neither is welding. Bolted flanges are stronger, form a better seal (even without gaskets or sealant), and can be quickly & easily disassembled & repaired. Once they're apart, it's easy to get a good weld all the way around. And they allow dissimilar metals, like mild-steel cats & pipes connected to a stainless muffler & tailpipe.

. .

 

[jperry1290]

Current set up is flowmaster 44s welded to aluminized tube, the welds look pretty crappy. I won't know till I drop the exhaust how that looks. The whole setup is supposedly only a few years old installed by the PO. I've heard a few other guys have issues with rusty flowmasters.

 

[73azbronco]

Dragging this back up as closest thread to my question:

I have a beautiful exhaust. Except I didn't notice it before the body went back on that it is one solid welded piece front to back. I need to install the EFI O2 bung, and I might as well throw a CAT in there as well while going EFI.

I have a 2 inch BL, frame off nice frame paint, underbody paint, etc. I don't want to mess that up.

How much of a mess are they going to cause welding a bung and or repairing a cut out section I remove to have them install an O2 and cat? My plan is to cut the pipe a foot or so after the location I need the O2 sensor, then unbolt and let a shop weld it in then use a sleeve to get it driveable back to the shop to put a flange on it. I'll probably do the same to other side to make it so the exhaust can be moved around if needed.

I'm 2 into 1, entering the muffler as 2. Unless they make cats around 6 inches long, that idea may be out

 

[Steve83]

I highly recommend you buy at least one mating pair of flat, gasketless exhaust flanges, and have them installed FIRST by cutting your 1-piece system, slipping the (bolted-together) flanges onto the pipes, & tack-welding in-place. Next, I'd have them cut it for the new cat, and tack-weld that in. Finally, I'd have them unbolt the flanges & drop both sections of exhaust for finish-welding & bung installation. Then you'll never have this problem again, and you'll be able to drop/repair/replace either section without cutting, or fighting U-bolted (leaky, noisy) joints.