The creation of a Stebro stainless-steel exhaust for a '63 Alfa 2600 Spyder
Before (front pipe)
After (front pipe)
The following is an account of a visit to the Stebro plant. The occasion was the final assembly and fitting of a Stebro stainless steel exhaust system. The car for which it was being custom built, a 1963 Alfa Romeo 2600 Spyder, had been undergoing a summer-long work interval in the underground parking garage of Franz Painer. Franz enjoys the ownership of a gorgeous fully restored and rebuilt '64 2600 Spyder, so he was very sympathetic to the project and donated this work space to me.
The exhaust story began when Stebro received an order from the U.S. for a stainless-steel exhaust system for a 2600. Andy Petszhenig, co-owner of Stebro, was in need of an accessible 2600 in order to make a prototype exhaust. As this car was up on stands already, and the current exhaust was badly in need of replacement, agreement on its use was quickly negotiated. Andy would use the car and its old rusted exhaust for measurements in the design of a prototype, and in return would install the shiny new stainless steel system he made.
This led us, on Saturday September 13, 1997, to Manotick, Ontario, the new site of Stebro (formerly of Carleton Place, Ontario). There, we were privileged to witness the birth of our new system: the final assembly, fitting and finishing at the hands of the master himself.
The prototyping of a new Stebro exhaust system starts with Andy's favourite job: making the plans using CAD (Computer Assisted Design) software. Using the CAD software and his painstaking measurements of the original, he creates three-dimensional drawings and directions that guide the staff in making the necessary bends in the metal (see diagram). The software also helps in creating a custom "jig" from a long piece of steel pipe. This jig cradles the exhaust during the manufacturing process, and has mountings that will tell the machinist if the bends are correct.
bending
the jig is up
In the shop there is a very large, very expensive bending machine not yet in service. One day, Andy hopes to be able to feed the data directly from his design software and into this automated bending machine, enabling completely computer-controlled production. He even hopes to be able to video-tape the old exhaust while it is on the car, and feed this info directly into the design program.
Andy's background is in electronics and mechanics. When he moved to Canada (from Switzerland), he augmented his knowledge of electronics and automation during his 10 years at Northern Telecom. There he was a technologist/engineer responsible for equipment such as a multi-million dollar ionic implanter used in manufacturing state-of-the-art "chips".
On the day of our visit, we began with the final grinding of the tip — an interesting piece. To most consumers it is visually the most important part of the exhaust. Maybe the only part — we have all seen those big goofy-looking trumpets coming out of the back of Honda Civics and the like.
Andy machines the tip from #304 stainless steel, which gives it a gold colour. It remains on the lathe for an hour or so, until all of the pits are eliminated from the rough steel. A fine grinding disc removes its outer surface as it rotates (see picture). In all there are 7 steps to finish the tip, the most challenging being the final polishing and buffing. It takes a delicate touch, and so far Andy is the only craftsman at Stebro who has been able to master the technique (see picture).
Grinding the tip
Andy's delicate touch
Care of the finished tip also requires discipline. No steel wool may be used as it would leave ferrous deposits that rust. If the tip gets dirty it should be washed with a mild dish soap solution. If there is a scratch, it can be buffed out with Auto-Sol. If it is properly cared for, "it will stay shiny for 100 years," Andy calmly states.
Like the tip, the flanges are #304 stainless steel. They are cut by laser at an engineering facility in Chicago. They are expensive but look wonderful with their clean lines. The pipe itself is made from #409 stainless steel, which cannot be bent with heat. A special bending machine must be used (see picture). This steel is so strong that in an accident the system will act to keep the car straight! I have seen a rear-ended Alfa GTV, which had its back end seriously pushed in — but the stainless-steel exhaust could be seen sticking out of the back virtually undamaged.
According to Stebro, features of #304 stainless steel:
- contains 18% to 20% Chromium and 8% to 10.5% Nickel.
- has excellent heat, oxidation and corrosion resistance.
- Looks great and "will shine for ever!"
- also made from #304 stainless steel: the flanges, internals and brackets
Features of #409 stainless steel:
- is specially designed for automotive exhaust systems
- resists atmospheric and automotive exhaust gas corrosion
- develops a light surface discolouring which will retard progressive corrosion
- contains 10.5% to 11.75% Chromium
Andy showed me the 2 pipes that make up the Alfa 2600 system (see picture). In every detail, it is an exact copy of the original as it was pictured in the Alfa Parts Manual (see illustration). On the front pipe, there is a small can and a muffler. This does most of the muffling. Then there is a tail pipe with another small can, which decreases the high pitched sounds. It is a free flow exhaust; if you stretched it out straight you could look right through it.
The fitting of the prototype was modified and refined over several trips back to the car. Care was taken to mimic the details exactly, including a right angle bend to the rear of the muffler. Even though the bend looks harsh, it is necessary, according to the perfectionist Andy. His rationale is that "someday this car may be in a concours, and that is the first thing they will notice." In show competition, points are lost if there is any deviation from the original.
The final assembly of the rear pipe required some welding (see picture). During our visit, a tig-welder was just having its bugs worked out. The challenge is producing a plasma at the welding site, so that all the metals melt as the two sides are joined. The temperature must be exactly right, or else the 4 or more metals in the alloy will crystallize and separate. The exposed iron crystals will rust, and the weld will eventually break. Ideally, a purple rainbow effect at the join indicates that the weld is uniform.
The final prep is a mild acid scrub. Stebro uses, of all things, Sani-FlushTM (see picture) as, in testing, it did the best job, even compared to expensive industrial products. It contains 0.2% sulphuric acid. The pipe is then washed with warm water (ideally at 60 degrees Celsius). The final result is a classy matte gray finish that will never rust.
After lunch, our crew moved to the site of the car. The front pipe installed perfectly. Everyone was happy. The rear pipe went on without a hitch, although Andy was not satisfied with it after it was on. He removed it in order to take it back to Stebro for some reworking, as it needed "a couple of degrees." I thought it was lucky that it was only the rear pipe that needed to go back, as I didn't think the larger front pipe would fit in Andy's Maserati. Andy, practical as ever, countered "Well, if I had to take the front pipe I would just put the top down and stick it out over the back seat." (Are you getting the visual?)
The finished system is beautiful, and will probably outlast several owners, and perhaps even the car. The Spyder's performance is improved, and the sound is a classic throaty rumble, muted to civilized levels. Andy is pleased with the prototype, and can now duplicate the system for other discerning customers.
In fact, everyone was very pleased with the day's accomplishments. It did seem like a lot of work to put into a car that was not owned by any of us (my father has the title), but Andy has been in these situations before. He smiled, "we are not doing this job for your father, we are doing it for the car."
Copyright © 1998 Tony Clunis
