In a previous post, I mentioned that the Dually Crew Cab would be getting a set of smoker stacks. This is the one page that tells you exactly how I did it, and how you can do most of this (if not all of it) yourself. 

The below assumes that you already have some exhaust work under the truck…  this article starts at adding the 90° bend from the exhaust up through the pickup bed.  On a `92 or `93 Dodge Ram D-series truck, the exhaust will probably need some minor rework.  I would also recommend a straight through muffler to minimize flow restriction. 

Also, this page assumes you are completely “ok” with cutting up the pickup bed and possibly part of the truck frame.  If you are not ok with that, DO NOT ATTEMPT any of this.  I have an older truck, so I was not concerned about keeping this truck  ”pristine.” 

Click on any of the images below to see a larger version!

Section 1 – Creating the Y-Pipe to split from one exhaust into two stacks. 

This involved purchasing two 3″ diameter, 90° bent 4″ radius tubes.   The goal was to create a smooth flowing Y-pipe or splitter pipe that would weld right up to the rest of the exhaust.  To get the two pipes to make a smooth flowing Y-shape, one half of one side of the pipe would need to be cut off of each part.  Then, the two pipes could be welded together to form a Y-shaped pipe. 

3" Dia, 4" 90° mandrel bent aluminumized tubing, marked for cutting one half side off, in preparation for welding

Making the cut in the mandrel bent tube.

An Orbital Jigsaw was used to make the cut on the 3″ Dia, 4″ 90° mandrel bent aluminumized tubing. An orbital Jigsaw is amazing; with the right blade it can even cut through pickup truck frames (and will do it about as fast as a plasma cutter)! 

This shows the first half of the cut in the 3" Dia, 4" 90° mandrel bent aluminumized tubing. There is a small burr along the cut line at the far right side of the part, which shows the top half has been cut with the orbital jigsaw blade. Just flip and repeat!

Pulling the cut piece off the 3" Dia, 4" 90° mandrel bent aluminumized tubing

Before the two pipes were welded together, I did some test fitting to see exactly how the smokestack setup would come together.  This was actually an important step to determine if I cut enough material off each side of the 90° pipes.   Better to cut off less and have to cut or grind a little more than to have cut off too much! 

Here's one way the pipes could be arranged to connect to the exhaust. In fact, this is exactly the way the pipes will be arranged on the 1992 Dodge Ram D-350 Dually Crew Cab

Another angle of how the pipes will be arranged for this smoker stack installation.

Depending on the arrangement of the exhaust on your truck, you could also set up the pipes this way. maybe with two 90° bends under the truck.

Now, with some mock ups out of the way, it was time to prepare the parts for welding.   Since they were aluminumized tubes throughout the system, I lightly ground the edges with a grinder to remove the aluminumized coating.  Then I made sure the two parts would fit together well and would fit the rest of the 3″ flanged pipes.  You’ll notice that one end of each part was flanged – this allowed for easy connection to the other parts of the system. 

A closeup view of how two of the 3" Dia, 4" 90° mandrel bent aluminumized tubing pieces will be welded together to make the Y-pipe.

Another view prior to welding the Y-pipe.

Here are the two halves of the Y-pipe arranged next to each other. In hindsight, I wish I had cut a little to the "removed" side of the line on each piece, because the finished pipe was just slightly smaller diameter than the standard 3" tubing.

Here's what the Y-pipe looks like when held up in mid air.

Time to weld!  Tack welds were used at first to set the right alignment of the tubes.   Then, once I was happy with the matchup of the two pieces, I welded them.   A wirefeed mig was used to make the welds. 

Here is the welded version of the Y-pipe.

Section 2 – Cutting a hole in the pickup bed. 

No fear!   Now was the time to pick the right spot in the bed for a pass-through hole, which would let the exhaust get up and out to the stacks.  The first step was to mock up the underside of the truck (align a piece of tubing with the existing exhaust and the bed) then drill a small hole centered on the location to be removed from the bed floor.  Once that had been done, I got up and went above the truck to mark the target zone and take some photos… 

This is a zoomed out shot of where the hole in the bed will be cut. You want to cut larger than the pipe by at least half an inch; this will allow for some movement of the exhaust while driving... and will avoid any banging or interference.

Underneath the truck, I did have to cut the frame. This is a crossmember that supports holding the front of the fuel tank to the truck. It was right where the pipe needed to go up through the pickup bed. After the truck was cut, I found an easy way to reinforce the crossmember and support it. The best way would be to weld angle iron to the crossmember and across the hole after the pipes are installed.

Here's a photo of the muffler and frame cut. Driving the truck around like this resulted in some resonances and drumming sound that were mildly annoying. In this photo you can also see where the front section of bed had just enough space for the tubes to pass between a sheetmetal reinforcement beam across the bed and the front edge of the bed.

Now that the hole was marked, and I double checked its location from top and bottom of the truck, I started to make my cut.  The easiest way to cut in a limited space location such as this is to first drill a 3/8″ or larger hole inside of the area to be cut, with the drilled hole edge  aligned with the edge of the cut line.   Then, insert the nose of some good quality tin snips (for a circle, you want red for left cut or green for right cut) and start cutting.   The bed sheetmetal was not too thick to be cut with the tin snips. 

The cut was made in the bed using a quality pair of tin snips. These are left cut (red), I needed right cut (green) also, for the other side of the hole.

This is the hole.... somewhat oval but in-line with the location of the cut in the truck frame. I may have enlarged it slightly more after taking this photo, depending on fit of the Y-pipe.

Section 3 - Attaching the Smoke Stacks to the Pickup 

Now that I had the hole cut, it was time to consider how the stacks would be attached to the pickup bed.  I had three requirements for this:
1.) The stacks had to bolt on, not weld on
2.) The stacks had to be firmly attached and not flop around while driving
3.) The stacks had to have some sort of isolation from the pickup bed… hopefully to eliminate any chance of resonance (vibration) or paint melting (heat). 

The next set of photos explain how I attached each stack using four auto parts store bought muffler hangers.  The hangers had a clamp end and a strap end, isolated using rubber pieces in-between.  I found similar straps at every auto parts store in town, so these should be easy to buy on your own, or you can get them from your favorite muffler shop. 

I used parts from inexpensive muffler strap type hanger to connect the stacks to the truck bed. Here's some of the parts leftover from cutting and drilling out the rivets on the hangers. The best hangers have a full C-lip for the clamp, not just an L-shaped lip.

Here are the muffler hanger parts. The best hanger is the one laying flat on the cardboard, on the middle-right. The other three (which are the same) don't hold as well onto the hose clamp (that extra lip on the bracket really helps hold it in position).

The brackets and rubber pieces were removed from the straps.  To do this, it was simply a matter of drilling out rivets between the various parts of the muffler strap, and then using a sharp cutting blade to cut the rubber pieces as needed.  I also added some paint to the brackets, because they were uncoated/unprotected (bare steel) as purchased.   Below are photos of how the stacks actually bolted on.  Note that I used a piece of rubber between metal components to avoid any metal to metal contact. 

The stacks are attached with the muffler hanger pieces and SST hose clamps (worm drive clamps). Home Depot had very good quality hose clamps in the plumbing section.

The lower clamp has a bolt going through the stake pocket bottom hole. I didn't even have to drill it out. I used fender washers between the rubber isolators and the nut. (Click to enlarge photo)

The front bedrail was drilled to accept the other muffler hanger parts. Self fusing silicone tape and a rubber isolator piece was used to prevent chafing or metal to metal contact. (Click to enlarge photo)

A photo of the passenger side smoker stack attachment. (Click to enlarge photo)

All this work to set up the stacks after I had cut a hole in the bed?   Yes, this was to check the height and to verify the alignment of everything before welding the system together. 

Both Smoker Stacks, as shown from the rear. When finished, the stacks will definitely need to stick up higher than as shown here!

This is what the stacks look like from the side of the truck.

Another shot of the smokestacks. The perforated heat shields (not shown) will make it look more like a big rig, and will prevent human contact with hot pipes.

This photo shows the perforated heat shield on the smoke stack.

Now that the stacks are in and the Y-pipe is ready, it will be much easier to see and to verify how everything should go together.  Notice the cardboard pieces under the stacks in the bed – I wanted to protect the chrome from getting chipped or peeling off the sharp bottom edges of the stacks.   These stacks came with header-type exhaust flanges but they were not used in my installation. 

This view shows the Y-pipe coming out of the pickup bed. You can start to see how the pipes can be routed to the stacks once they are moved up into the air.

Floor or bed level view of the Y-pipe. It will sit higher than this when welded up.

Photo taken from underneath the truck, view from passenger side.

This is looking straight up at the bottom of the Y-pipe. It passed right through the hole in the bed and has clearance going through the frame.

A simple 90° bend will be all that is needed to make the turn from the muffler up into the bed. Mandrel bends ensure that there are no flow restrictions to the hot, pressurized exhaust coming out of the muffler. Dodge used mandrel bends from the factory for the entire stock exhaust system.

Section 4 - Welding pipes from the muffler to the stacks. 

Admittedly, I didn’t do the work shown below – my local muffler shop did the work.   I figured they could provide the remaining tubing, align everything, and then weld it all together for me.  If I were to do it over again, I could very easily have purchased a couple more tight 90° bends from the mandrel bending shop, a couple straight pieces and had them all shipped to me for welding.   This would definitely have been the cheapest route and allows full control over the finished product.  But even with help from the muffler shop, everything turned out well and has minimal overall flow restrictions considering the two pipes are branched off  of one.  Add four clamps, a few welds and it was all done.  Of course there was some welding underneath the truck too…. 

Here's the work all finished. The pipes between my Y-pipe and the stacks were done by the muffler shop. All tubing is aluminumized.

Clamps were used to ensure a tight seal, considering the side closest to the bed walls could not easily be welded.

In retrospect, the muffler shop had to use a standard pipe bender which made a significant restriction at the bend. The restriction probably doesn't harm performance (since there are dual stacks coming out of one 3" pipe) but ideally these would be mandrel bends as well.

The Y-pipe to side tubes uses clamps again because the weld could not be made all the way around the tubing from inside the truck bed.

The heat shields are also attached via hose clamps (worm drive clamps). I can't say this is the best design in the world, but they work. When I reshaped them to fit the stacks, I could hear some chrome crackling, so I hope the coating lasts a while. Let's see how long they last before they rust!

The pipes underneath the truck are shown here. The muffler shop was kind enough to spray the pipes and welds with cold galvanizing spray to further protect them from any future corrosion.

In these photos, you’ll notice that there is a flexible coupling joint in place near the hole in the bed.  I was concerned about vibration and flexure between the underside pipes and the top of the truck.   This flexible coupling (fully sealed with accordian type tube inside the armored section) helps to take up any misalignment or flexure as I am driving the truck.  Not to mention any possible thermal expansion considering these pipes receive 1,200 °F  air from the turbo when I am pulling a trailer uphill. 

The flex joint was added to prevent undue stress on the topside pipes if any movement was encountered by the chassis pipes.

Photo taken as viewed from passenger side rear dual wheel.

Sources:
Mandrel Bent tubing and the flexible coupling:  Columbia River Mandrel Bending  – http://www.mandrel-bends.com – Great service, they ship fast and you can order on-line!
Smoke Stacks:  http://www.jcwhitney.com
Hose Clamps:  Local Home Depot store
Exhaust Hangers – O’Reilly Auto Parts and Auto Zone. 

Copyright Kris Wickstead ©2010.  Do not copy or reproduce without permission.