Your 4x4’s exhaust system has plenty to do getting spent fuel and air out of the back of your rig. Modifying suspensions or drivetrains for off-road performance and reliability on the trail makes factory parts inadequate or just in the way. We have spent our fair share of time underneath 4x4s cutting and splicing exhausts apart and back together when things had to move for that solid-axle swap, new skidplate, or after that rock on the trail adjusted the factory tin can muffler. Also, who doesn’t like to hear a bit more of a rumble from under the hood? Your 4x4 is more than just a commuter—it’s a toy, and who doesn’t want to hear their toy making a little noise? Sure, you could throw a bunch of money at a custom exhaust shop, but if you are cheap like us you want to save a few bucks. Over the years we have learned a few tricks and tips that may just help you get your rig back together and back out on the trail with as few exhaust leaks as possible and a little change in your pocket.
As you know, we love everything 4x4. We love tools that make our lives easier, and we love reasons to buy tools. Dabbling in exhaust building is one such reason. You can get by building exhausts with a hacksaw, handtools, and a few specialized tools and tricks (we will show you later). Also, it’s amazing what you can create with a hacksaw and passel of exhaust clamps, but occasionally a MIG welder is a must for exhaust building. Also, a chop saw or a band saw helps a ton and can “up” your exhaust game quickly, yielding more professional results. If a welder seems extravagant to you, then a mandrel exhaust tubing bender and a flaring machine are probably out of the question. Sure, they would be nice to have, but with a few tips and tricks there are a ways around spending the tens of thousands of dollars these machines command.
Aftermarket mandrel-bent universal dual exhaust kits are a great source for parts when you need to build a full custom exhaust for your 4x4. These kits are available from a variety of exhaust companies and aftermarket parts suppliers. You can get them in diameters ranging from 2 inches all the way up to 3 1/2, and since they are universal they are designed to include enough pipe for very long cars and trucks from the 1970s. That means on a shorter, smaller 4x4, or on cars where you are only running single exhaust, or an after-cat system, the kit can yield enough bits to build a few exhausts. This kit is from Summit Racing Equipment. It’s a steal at $219.97 for a large amount of 2 1/2-inch aluminized steel. We have used this to build almost two complete 4x4 exhausts (with the addition of a few mufflers) and still have parts left over. These kits are also available in raw steel, aluminized steel, chrome, and stainless steel.
You can also buy mandrel-bent pieces individually for smaller projects where you have a fair idea of what you need. For this solid-axle swap on an S-10 Blazer (more about this in an upcoming story), we had to move one of the downpipes from the 4.3L V-6 a bit closer to the transmission bellhousing to clear the front driveshaft. The easiest way to do this was to make a few cuts in the stock Y-pipe and add in two 2-inch-diameter aluminized steel 45-degree mandrel bends from Summit.
When we modify our 4x4s for off-road use, sometimes parts of the exhaust need to be changed or moved so everything will fit. Solid-axle swaps are one major modification to lots of systems on a 4x4, and the exhaust is one of them. When we did an SAS on our 2005 Chevy Tahoe, Rosco P. Drivetrain, we had to make room for the front driveshaft. That meant cutting up the factory Y-pipe to rotate and move one of the pre-cats, and then adding a new crossover pipe. By cutting at the arrows and tuning how the tubes butt together, we were able to get the Y-pipe back together without reinventing the wheel or adding a ton of new parts. The only new parts were the exhaust flange donuts and the shiny section of 2 1/4-inch tube for the crossover.
If you are a real cheapskate you can also cut up and reuse old exhaust pipes, pie-cutting bends and cutting angles to cobble something together that might just work to fix your exhaust after a new skidplate or drivetrain swap. If you live by a custom exhaust shop you can also beg, buy, or steal pieces of exhaust that they have discarded. Sometimes a shop will mess up a bend and have to start over, and the part that is junk to them may be just what you need. Lastly, if you have a pal with a tubing bender for bumpers, rollcages, and general fabrication, you can always bend up a super heavy-duty exhaust out of welded-seam 0.095- or 0.120-wall tubing. Only expensive benders will bend thin exhaust tubing without flattening or otherwise deforming it as shown on the bottom. You can pack the thin-wall exhaust pipe with sand and see if that works. We don’t have time for that.
A couple of times we have run into 4x4s where the factory exhaust after the cat was either damaged, in the way of that new skidplate or shocks, or just inadequate. Big, heavy, quiet, thin-walled mufflers are fine for the factory, but drag them over a rock or two and you will need to make repairs—that is, if they are still attached to the vehicle. Here we replaced a huge damaged muffler on a Kia Sportage (fourwheeler.com/how-to/body-chassis/1602-kimchi-the-kia-rehash-after-ctc-2015/) with a cheap small muffler from the local parts store. By reusing bits of the old exhaust we were able to build a mini exhaust for Kimchi with our only investments being time, labor, and the cost of a cheap muffler.
Swapping out your exhaust for a heavy-wall muffler like a Flowmaster not only improves the sound of your 4x4 but makes it more durable. We have bashed Flowmasters on rocks for decades, and a side effect of their construction (and unique sound) makes them very durable for 4x4s. Also, we have saved a few pounds ditching the complicated factory tailpipe. For us a heavy-duty muffler and a turndown fits with this S-10 Blazer build well.
For our S-10 Blazer we dropped the huge muffler and tailpipe and then cut the mounting flange off the front of the old muffler to weld to our 50-series Flowmaster. Mock up everything in place, and start welding things in place, keeping in mind that you may have to remove part or all of the exhaust system to fully weld the seams.
Exhaust systems gain weight fast and must be supported when you plan on haulin’ oats over rough terrain. Here we repurposed the factory muffler hanger to hold the back of our new Flowmaster and the front of the downpipe. With a little work this factory-engineered exhaust mount was free.
Sometimes you need a new exhaust hanger. We got these Walker Exhaust Hangers (PN 36518, on the right) from Summit after a friend recommended them. You can bolt one end to the frame and cut the other end to length, bend it, and weld it to exhaust pipes or mufflers. The other hanger came in a stainless steel dual exhaust kit from MagnaFlow. The kit had more hangers than we needed, so we kept the leftovers just in case (and our neighbor calls us a hoarder—pffft!). Both have nice strong rubber bushings that eliminate exhaust vibrations while supporting the exhaust.
If you’ve spent any time at all at a custom exhaust shop you may have noticed that their fancy tubing bender machine has a hydraulic tube or pipe flaring tool. By adding a flare, or buying tubing with a flare already on it, you can get a few degrees out of a junction between two pieces of pipe. This can help make up for slight bends that you are going to run into.
If you need to add a flare to a piece of tube and you don’t have a pal at the local exhaust shop willing to flare it for you, you can buy a cheap tool that will flare most pipe. The results of using this exhaust flaring tool vary with experience and what you are trying to do with it. We have had the tool in this picture for several years, and it is showing some wear, but it still works as well as anyone can expect. To flare or bring oval’d exhaust pipe back to round, insert the tool in the pipe and tighten the black driver portion with a flat for a wrench. Once things get tight you can whack the black driver portion with a hammer a time or three and try to tighten it some more. Rinse and repeat. You will have better luck with the pipe still on the vehicle or held firmly in a vise.
This relatively inexpensive band saw makes very nice cuts in exhaust tubing as well as other metal objects we are modifying. While it could be replaced by cheaper tools, we use it all the time. You can make angle cuts that make an at-home custom exhaust look almost professional.
For a fairly effortless and true cut in round (not deformed) exhaust pipe, a large tubing cutter like this is great. If you have to, you can also get pretty close to a flat cut if need be with some masking tape and a hacksaw.
Jackstands, pieces of wood, cardboard (to serve as a spacer), ratchet straps, and more can be used to mock up your new-to-you exhaust parts. Keep in mind that exhausts move and thus need to have a little space between themselves and the other parts of your 4x4. Using our fat fingers as a gauge (we are estimating they are 1/2 to 3/4 inch thick) to allow for things to move is a good rule of thumb (see what we did there?).