1. When done with care, plumbing can be a real feature on high-end car builds.

By Ron Covell Photography by Jay Doerfler

e are continuing our investigation of the inspiring work being done on the 1969 Camaro project being built by Auto Body Specialists in Manchester, New Hampshire. In this installment, we’ll take a close look at the extensive stainless steel hardline plumbing and the all-stainless exhaust system.

Stainless steel is sometimes called the “queen” of metals because it does not rust and is non-corrosive. If you polish or brush the surface to a high luster, it will usually keep that shiny finish for many years. That’s why stainless steel is widely used in industrial kitchens and surgical tools.

But stainless steel is a tough material to cut, and the fitup of joints is critical. Any defects in the joint fit will require extra heat and filler rod to flow together, and because stainless steel distorts much more than mild steel or aluminum, it’s essential to keep the heat to the absolute minimum. It requires top-notch welding techniques to make leak-free joints for plumbing and exhaust systems, and Jay Doerfler, the owner of Auto Body Specialties, is a master welder, as you will see in the photos.

For first-class work, the inside of the tubing should be purged with argon gas. Argon is heavier than air, so the proper method must be used to remove all the air from the tubing before welding. Usually, a cap is placed on the highest end of the tubing, with a flexible line connected to an argon regulator. The lowest end of the tube also needs to be capped, but a sealable vent must be provided so the argon can force the air out the bottom. After all the air is expelled, the bottom vent is sealed and the weld is completed with the tube filled entirely with argon gas. Not properly purging the tubes will lead to a granular weld, which may be prone to failure.

Small sizes of stainless tubing can be successfully bent using hand-operated tools, but for sizes over 5/16 inch, the hand tools must make a relatively large-radius bend to avoid wrinkling. These large-radius bends work well in many cases, but when multiple tubes need to fit into limited spaces, tight-radius bends are often better. The best way to get these is to buy a selection of mandrel-bent tubing and cut sections from them to join with straight pieces. When finished properly, these welds can become nearly invisible—a sign of expert craftsmanship.

Stainless exhaust systems are assembled in a similar manner, using sections of straight tubing connected to mandrel-bent 45-, 90-, and 180-degree bends. Finding enough space to run an exhaust system under a car is usually challenging. It looks unappealing if the tubing and/or mufflers are visible from the side of the vehicle, and there are many obstacles the exhaust must clear, such as chassis crossmembers, the fuel tank, the driveshaft, the rear axle assembly, and other components. The larger the tubing, the harder the routing becomes. A high-quality job is characterized by an exhaust system that’s neatly tucked out of sight and has a smooth visual flow. The photos showcase an exemplary build of a complete stainless exhaust system, from the Detroit Speed headers to the custom-fabricated exhaust tips.

3. With larger sizes of tubing, such as the 3/4-inch-diameter material shown here, manual benders are only capable of making large-radius bends. While there are cases where a large radius bend can be effective, for high-precision applications, the tighter radius of mandrel bends is often the best approach.

5. Here, two tubes are being fitted simultaneously to ensure they run parallel. Masking tape helps hold the tubes in place as the joints are carefully fitted. Once the fit is dialed-in, the tubes are tack-welded together.

7. Plumbing requires high-quality welds; it’s essential to get full penetration.

9. With the welds finished and smoothed, the installation looks extremely clean and professional. These black-anodized 45- and 90-degree AN fittings are made by XRP Fittings.

11. Longer runs of tubing require clamps to prevent movement and chafing. Single clamps are shown on the top, and two single clamps have been joined to make the double-tube version shown below.

13. Stainless steel exhaust systems are typically constructed from straight lengths of tubing and mandrel bends. This is a 3-inch Stainless Works Rod Builder Kit and an X-pipe.

16. Stainless exhaust tubing should be purged with argon while welding, and if done correctly the inside of the weld flows together cleanly. Note the perfect penetration on this joint.

17. These are the tubes that run from the headers toward the mufflers. It’s good practice to add a “crossover” in an exhaust system with two banks of cylinders. This helps balance the exhaust pulses on both sides, thereby reducing backpressure and enhancing combustion efficiency. Temporary pieces of rectangular tubing are used to hold the pipes in alignment as the assembly is fitted into place.

19. Here, the tight-radius sections have been joined to straight pieces of tubing and sections cut from U-bends. The welds on the rear tube have been ground smooth.

21. These are the tubes that arch over the rear axle.

23. Here, the large flange on the tubing is bolted into place on the inner panel. There is a similar mount for the tailpipe on the back side of the panel. Note the flexible connection, which accommodates the change in length as the stainless tubing heats to working temperature.

24. Behind the rear axle, the exhaust tubing increases in diameter and transitions from a round to a rectangular shape. Note that another expansion joint has been fitted into place.