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Building a Custom Exhaust at Home for Cheap

Posted in How To: Tech Qa on January 4, 2018
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Let’s face it: Any and all 4x4s with internal combustion engines fart out spent gases at an alarming rate, sending thousands of little gas balls out the rear of the system. Generally most car people enjoy the smell of exhaust, but only in small and controlled doses. It’s crazy to think that these machines we love use a spark of electricity to turn liquid fuel into rotational force and somewhat stinky air. That means that all of our rigs (except that electric rockcrawler you have secretly been building) require an exhaust system to control the sound of in-cylinder explosions and provide a safe point of egress for the spent gases.

Dino, our dinosaur of a 1970 Chevrolet Suburban, is no exception. After 48 years of hard use Dino’s stock exhaust system was in bad shape. This lumbering beast rolled off the assembly line with ram-horn exhaust manifolds feeding into a 2-inch-diameter Y-pipe that joined into a single 2-inch-diameter choke pipe, which had to run a mile and a half from the back of the transmission, through a coffinlike muffler, and eventually out the back of the truck. Did that sentence take forever to get through? So did Dino’s exhaust gases. Plus, years of abuse had rattled, dented, and broken the exhaust into about two miles of restrictive 2-inch rusty gopher tunnels. What exhaust manifold gaskets still resided between the cylinder heads and ram-horn manifolds were filled with holes, and the seals and gaskets at the collectors had mostly blown to bits long ago. The result was exhaust leaks galore and an ever-present scent of Dino farts.

In an attempt to prolong Dino’s life and make the truck more drivable both on- and off-road (with less carbon monoxide intake), we decided to rebuild Dino’s fart tubes from the manifolds back. The best part is we are doing all this with a mix of leftover exhaust tubing from previous projects mostly at home with only a little help from the pros. If you have a welder and some time you can do this too. And if you don’t happen to have a whole pile of mandrel bends kicking around your workshop, Flowmaster not only offers high-quality fully welded mufflers that sound killer but also has a U-Fit line of do-it-yourself tubing kits for single- or dual-system applications in varying diameters to make your exhaust building session a breeze.

We started our exhaust rebuild addressing any potential of blown-out gaskets that would allow upstream exhaust leaks. That included refurbishing the exhaust manifolds to the best of our abilities. The studs that held the collectors and donut gaskets in place were eaten away by rust, heat, and age. We carefully extracted four of the six studs. We had to drill and retap the two stubborn ones that refused to cooperate.
We have built a few exhaust systems ourselves and have seen several more built at professional shops. One thing most shops almost always do is reuse the first few inches of the factory exhaust system since it’s already there, providing it’s in good shape. We did the same, cutting about 8 inches back on one side and about 12 inches on the other. We then took these bits of exhaust to our local exhaust shop and asked the guys behind the counter to use their exhaust machine to flare the new cut ends a bit so we could weld on some 2 1/4-inch stainless exhaust tube we had left over from another project. We brought a small piece of the stainless so they could test-fit the joint.
With these bits of old Dino’s exhaust flared, we cleaned them up a touch and applied some high-temp paint from our local auto parts store. We’ll talk more about this paint later, but the idea is that it will help resist any future rust from easily forming. We installed the manifolds to the engine using factory-style gaskets from Fel-Pro and then attached the exhaust collectors to the manifolds using new parts-store donut gaskets and new studs. You want the donut gaskets that are soft and made of graphite.
The small bits of Dino’s original exhaust gave us a starting point to use some 2 1/4 stainless bends and tubing we had from a long-past Jeep project. These pieces came from a universal dual exhaust builder kit from Summit Racing Equipment. Since we originally used the kit to build a single exhaust system on a short Jeep, we had a ton of pipe left over—perfect for a project like Dino.
Our plan was to recreate the original exhaust Y-pipe’s design using the larger 2 1/4 stainless pipe we had on hand. Since we had a template to go by, we could easily cut the stainless mandrels to mimic the bends in the factory Y-pipe. We also had to build a two-into-one for our Y-pipe. That was easy with the help of a 2 1/8-inch hole saw and our Miller Electric Welder.

Here is the first part of our custom exhaust for Dino. We built the Y-pipe in place on the truck, tacking pieces into place until this section was done. We then welded what we could with the part in place on the truck and then removed it to finish-weld the joints between the bends and straight bits of exhaust pipe. Flares allow a little wiggle room when you’re joining things together and you can always cut a pie piece off a mandrel bend to help keep the tube joints tight. We used a permanent marker to mark for the cuts and then a horizontal band saw to make nice flat cuts in the tubing. These should make welding the pipes together with our Millermatic 190 easy (see our review of the 190 here).

With the Y-pipe installed we could move on to building the rest of the exhaust. For that we would use parts of a 2 1/2-inch aluminized steel exhaust kit from Summit Racing Equipment that we originally got for Editor Hazel’s UACJ-6D build. Again that kit was intended to build dual exhaust on a big old honking American muscle car, and we used part of it to build a single exhaust system on a long (but relatively short) Jeep. For Dino we will use an exhaust clamp to join the stainless Y-pipe to the rest of the exhaust. This will allow us to remove part of the exhaust instead of all of it if we need to work on the transmission or something.
Looking the other way down that long section of 2 1/2-inch aluminized pipe you can see that we played around with the idea of using a very rare Ray Flueger–series Flowmaster Muffler that Hazel brought to us. The muffler was originally earmarked for the UACJ-6D but went unused because we feared the Cummins 2.8L would be too loud breathing through it. Similar concerns faced us with Dino. More importantly you can see how we used jackstands to hold the exhaust in place as we fitted each subsequent piece in place. The key is to assemble everything loosely, making adjustments as you move back. Once you are happy with how something fits you can heavily tack-weld it in place and move to the next part. You don’t want to finish-weld until you are positive everything is in its final place.
Building the section of Dino’s exhaust that passes over the axle was the hardest part of all this. For one, the pipe has to go up to clear the axle upon compression, and it also has to weave around shock bodies and eventually the gas tank to run out under the driver-side rear framerail. We were able to achieve this with two 45-degree bends from a Flowmaster U-Fit system we had used on another project that twisted to jog out and then back in, along with one 90-degree bend directly over the axle.
With much of the exhaust system built we welded what we could in place on the truck and then had to pull it out to finish-weld. Snaking the Y-pipe, and then later the tailpipe, in and out of Dino was fun—if you want to call it that. You will also notice that we ended up using a quieter turbo muffler in Dino and will save the rare Flueger-series Flowmaster for an extra-special project down the road.
We have definitely learned a lot from the people around us and hope to continue that trend. One person who has helped us learn a lot about exhaust work is our fabricator extraordinaire and Ultimate Adventure crony pal Dave Chappelle. He tells us what gaskets to use and where, how to add hangers (for Dino we mimicked the hangers from the original exhaust), what mufflers to use, and more. This is one tip we picked up from him a few years back: Coat your fresh welds on aluminized steel with high-temp paint. That should help stave off rust for a few years to come.
The last section of Dino’s new exhaust is a 90-degree bend next to the gas tank and a slight turn downward just under Dino’s left rear quarter-panel rocker. This helps get most, if not all, the gases out from under Dino before they can seep inside the cabin. Also, with the tip just inside the rear quarter rocker, if we bang the tailpipe on a rock it will not get crushed between the sheetmetal and the ground but should sneak up inside the body and out of harm’s way.

Sources

Miller Electric
Appleton, WI 54912
920-734-9821
www.millerwelds.com
Summit Racing
Akron, OH
800-230-3030
http://www.summitracing.com
Fel-Pro
Southfield, MI 48034
800-325-8886
www.felpro-only.com

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