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Exhaust System Install - Twistin' TubeTube B Or Not Tube B, That Is The Question From the January, 2011 issue of Rod & Custom By Kev Elliot
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When it comes to installing an exhaust system on a project vehicle, there are a number of options open to you; though it's a safe bet to assume no production system is going to fit. It's also safe to assume there'll be a lot of custom fabrication. You could take your car to a muffler shop that will be able to bend up a system to suit, though the end result may not be as attractive as you'd like, as exhaust bending equipment distorts the tube when it's bent and reduces the diameter as it does so. However, if a car is not detailed underneath, and will be driven a lot, this is a viable option. You could also adapt an existing system if your car is not too far modified from stock. The starting point for any... The starting point for any exhaust system is a good pair of headers. Mine came from Sanderson and are block huggers, with an aluminized ceramic coating and supplied with collector flanges, hardware, and a high-temperature RTV silicone gasket. Sanderson claims they are the tightest fitting header available. Various primary tube diameters, from 1 1/2 to 1 7/8 inches, are available depending on the horsepower of the engine. This is certainly not the case with the Purple Pig project '49 Chevy, meaning I had to fabricate a system from scratch-a system that would have to take a tortuous route in order to clear various components, and would consist mainly of sections of U-bend welded together with straight lengths comprising the rear sections and part of the passenger side system. My preferred method, having done this a number of times in the past, is to buy a number of mandrel-bent U-bends and a length of straight tube. I elected to run 2 1/2-inch-diameter tubing front to rear, and purchased 10 U-bends and 10 feet of straight tube. As it turned out I needed one extra U-bend of a smaller radius, but was left with only one 3-inch section of U-bend at the end. The headers I used are block huggers from Sanderson Headers, which are very compact, and are advertised as offering clearance for any motor mounts, tie rods, or steering rods. Also, any starter and transmission combination will clear this header except cast-iron Powerglides, as will any rack-and-pinion. Perfect for my application! The headers were supplied with a polished, aluminized ceramic coating, which reduces engine bay heat and improves cylinder scavenging. Sanderson headers are designed... Sanderson headers are designed to be installed without conventional gaskets; a bead of RTV silicone is all that's required. Muffler choice can either make or break the driving experience, being either too loud or too quiet, as well as droning on the highway. With this in mind I opted for Patriot Exhaust Products' new VaraFlow muffler, which features an electric motor and valve, allowing the driver to adjust the volume and tone, whilst on the move. Constructed from polished stainless steel, the VaraFlow measures 23 1/2 inches overall, with the muffler body 18 inches long, and has a 2 1/2-inch inlet and outlet. The compact size was advantageous as there's not a lot of room under the '49 for large mufflers, or anything else come to think of it! When fabricating a system using U-bends, care should be taken to ensure every cut is absolutely perpendicular to the tube for close-fitting joints, especially important when TIG welding. The tube should also be cleaned on the inside at every joint, and any swarf blown out of the tubing using an airline before welding. Also take into consideration that the exhaust generates heat, so plan the route carefully to avoid close proximity to gas and brake lines, and components such as the starter motor, gas tank, and brake master cylinder. Pay attention to suspension travel limits, especially around the rearend, and ensure you don't mount the system too low. I managed to keep this system tucked up close to the floor and above the lower edge of the chassis rails. Now the system is tack welded together, I have the laborious task ahead of me of removing the rearend, taking the whole system off the car, finish welding it (though this is done on the front section), having it coated, and refitting it and the axle. Then, finally, I can fire the motor, bleed the brakes ,and drive this puppy. 'Bout time, too!  A band saw was used to cut...  A band saw was used to cut the bends to their desired length. This produces a straight cut, though care must be taken to ensure it's perpendicular to the radius of the bend, otherwise odd-looking joints will result.  The first step toward fabricating...  The first step toward fabricating the system once the headers had been installed was to bolt the flanges in place.  I elected to tackle the driver...  I elected to tackle the driver side first, coming off the flange with a 90-degree bend, formed by cutting one of the 180-degree mandrel bends in half.  In addition to ten 2 1/2-inch-diameter...  In addition to ten 2 1/2-inch-diameter mandrel U-bends, I also bought a 10-foot length of straight tube. This tubing cutter made light work of producing perfectly straight cuts. Unfortunately, it can only be used on straight tube!  I also used this hand-held...  I also used this hand-held 18V mini band saw by Masterforce during the project. Care once again was required to produce perpendicular cuts.  With practice, cuts can be...  With practice, cuts can be determined by eye, but a square can be used to mark the bends for cutting at established angles. Note the mark on the tubing (arrow) for a 45-degree cut.  A drum sander in an air drill...  A drum sander in an air drill was used to clean the inside of each piece of tubing once cut. Not only did this remove any burrs left from the cutting procedure, but removed any oil residue from the tubing. TIG welding requires the metal to be clean and residue-free.  Each section was tacked in...  Each section was tacked in place using a TIG welder before moving to the next. Three tacks on each joint were sufficient to hold them in place, with final welding coming later.  Moving to the bench, this...  Moving to the bench, this section was fully TIG welded before being reinstalled to move to the next section.  The underfloor master cylinder...  The underfloor master cylinder necessitated the exhaust be routed around it before passing through the trailing arm mounting crossmember. It can clearly be seen that this whole section is fabricated from lengths of the U-bends.  Here I'm navigating the tubing...  Here I'm navigating the tubing around the oil filter. Note the two Sharpie marks that allow the tubing to be aligned for welding, as well as the tight tolerance of the butt joint.  Here's the first part of the...  Here's the first part of the driver side tacked together. I tried to keep the tubing away from wiring and brake lines as much as possible.  I installed a three-bolt flange...  I installed a three-bolt flange just aft of the trans crossmember since if the front section was any longer it would be impossible to remove. Fabricating the system in three sections on each side also means it would be easier to have high temperature coated before it's installed for the final time. The flange was mounted at the angle shown, rather than the more conventional angle of one or two of the boltholes at the bottom, as it fitted the limited space available this way, and let's face it, no one's ever going to see it once the car is done!  This is the front section...  This is the front section of the passenger side system (shown because it demonstrates another way of aligning the sections of tubing), allowing more than one section at a time to be trial fitted before welding. I wrapped each joint with masking tape and then cut sections out to allow the joints to be tack welded.  The passenger side didn't...  The passenger side didn't require the system to be routed around any obstacles such as the master cylinder, so a long straight section could be used, but again required a flanged joint in order for it to be removable. Wanting the straight section to remain just that-straight-I spaced two flanges with washers, and tacked them in place on the solid length of tube, before cutting the tubing between the flanges.  Once through the rearmost...  Once through the rearmost crossmember, the exhaust was routed up and over the trailing arms. Note the length of 1x1-inch box section (arrow) placed across the arms to ensure the tubing was at the same height on both sides, as well as the Sharpie marks again, ensuring the joints were aligned during welding.  Wanting the system to be as...  Wanting the system to be as symmetrical as possible, and of an equal height on both sides, I supported it where I could during the fabrication process. Here I used a length of box section and part of a U-bolt clamp where it passed through the trailing arm crossmember.  Looking into the muffler,...  Looking into the muffler, it can be seen that the electric motor operates a butterfly valve, forcing the gases to run through the outer muffler when closed, but providing straight-through pipes when open. This system is more compact, neater, and requires less tubing than the Y-type cutouts. The valves mean the mufflers can be adjusted to provide the exact sound required, as well as to tune out annoying drones when driving down the highway.  I elected to install the first...  I elected to install the first of three mounts at the crossmember. The bushes and brackets were sourced from a local muffler shop, while the lengths of rod welded to the tubing are actually parts of rear axle U-bolts, which handily already incorporated bends.  I'd decided to run the exhaust...  I'd decided to run the exhaust over the trailing arms as not only would it make routing it over the rearend much easier, but offered the best location for the mufflers, away from the fuel, brake, and air lines. The mufflers are stainless steel items from Patriot Exhaust Products, and incorporate electric cutouts. They are supplied with a simple two-wire hookup with a shielded harness.  With the mufflers supported...  With the mufflers supported at the same height and angle on stands, I used a couple of 12-inch steel rules to space them apart, holding everything together with masking tape while I mounted them. As I'd been thrashing to get the '49 on the road for the STREET RODDER magazine Road Tour to the NSRA Nationals, I was going to turn the pipes down as shown and temporarily terminate the system here.  With the mufflers mounted,...  With the mufflers mounted, the system was finished. Unfortunately, the rest of the car wasn't and didn't make it to the Nats-I did though.  On my return from Louisville...  On my return from Louisville I decided to route the exhaust out the rear of the car as originally planned, meaning I had to snake the tubing over the rearend through very limited space, though I'd allowed sufficient when mounting the ShockWaves, fuel, brake and air lines, and suspension level sensors during the build. Here I'm tack welding the rear section together.  This is what the rear of the...  This is what the rear of the system would have looked like had I had time to get the car finished to drive to Louisville. The tubing follows the angle of the trailing arms before entering the mufflers.  Snaking the tubing over the...  Snaking the tubing over the rearend involved more twists and turns than the average soap opera plot. I shall wrap this section with Thermo-Tec heat shield, as used on my roadster pickup, as it does run close to brake and air lines, as well as the ShockWaves, in a couple of places. Here the ShockWaves are fully extended, meaning this would be with the suspension fully raised while this would be in the fully dropped position. The car will never be driven at this height, but even so, the exhaust does not touch any other components. When routing an exhaust, always allow for suspension travel when routing the tubing over, or even under, a rearend, or near suspension components.  Looking from directly below,...  Looking from directly below, you can see the route the tubing had to take to go over the axle. I also had to move the mufflers forward by some 5 inches in order to gain enough room for the bends to clear the ShockWaves.  The rearmost section of the...  The rearmost section of the system would comprise a length of straight tube, exiting between the gravel pan and rear chassis crossmember, and ultimately through the rear bumper. Knowing the height and position of this length of tubing, I needed to make one last bend to connect it up. When cutting U-bends, an adjustable protractor can be used to determine the angles of the cuts.  I needed a bend with a tighter...  I needed a bend with a tighter radius to make this final turn, returning from a quick trip to the mandrel bend supplier with the bend shown on the right.  Here's the rear of the system,...  Here's the rear of the system, with both tailpipes running alongside the sunken trunk floor, as planned. I had to sacrifice a little symmetry when it came to routing the exhaust under the Panhard rod on the driver side, but everything is tucked up above the lower edge of the chassis, meaning I'll never rip my exhaust off when traversing steep ramps or suchlike.
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