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Exhaust system pipe material variations

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I'm asking about tonal variation created by various exhaust system materials.  


I'm aware of three types of exhaust pipe materials; uncoated steel, aluminized steel and stainless steel.  then I've noticed at least two different wall thicknesses or gauges of pipe materials.  Most manufacturers of exhaust systems don't disclose the gauge of pipe they use, but a decent muffler shop will have thin gage for low cost sales and a heavier gauge.  I've got a very heavy gauge uncoated steel pipe on the 1940 Super that I'm working on and the sound of the engine is terrific through a muffler that appears as a standard replacement.  I suspect the light gauge pipe material would sound different based on the idea that musicians can get very critical of the manufacture of their brass instruments.  


Is there a noticeable tonal difference between the different materials and gages?  What gauge pipe material is most desirable for originality?

Edited by kgreen (see edit history)
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Stainless does tend to be a bit throatier for reasons I can't explain. When I was with a Corvette tuner, we sold two versions of our ZR-1 custom exhaust system, one stainless and one mild steel, and they definitely sounded noticeably different despite being made by the same guys on the same jigs. I suspect the stainless is a bit stiffer and that changes the resonance of the entire system. It's slight, but you will hear a difference.


My Limited's exhaust is pretty quiet, but I just added a second muffler to tone it down even more and it's 100% stainless. I liked the sound but there was a drone on the highway that I wanted to eliminate and while the rumble at idle was pretty cool, it was out of character for a limousine. The mild steel system that was on it previously was far quieter and did not have the drone, even though the muffler was ostensibly the same size. The only difference was the material (although internal muffler construction may have played a part--I don't know who supplied the old muffler). I am quite satisfied with the sound now with two mufflers on the car--idle is deeper yet quieter, cruise is silent.


Others have told me the same thing about stainless being a bit louder. Doug Seybold installed a beautiful 2.5-inch polished stainless system on his 1940 81C, and that thing sounds like my Mustang 5.0. When I asked him about what kind of system to install on my car, he said he didn't usually use stainless for that reason and typically recommends and installs mild steel systems on customer cars.


Personally, ,my opinion is that if you're installing an off-the-shelf standard exhaust system, go with mild/aluminized steel. Cheaper, quieter, and on a collector car it'll still last many, many years. That's what I used on my 1929 Cadillac. It sounds appropriate with a nice burble but still Cadillac quiet. I use stainless on cars with custom exhaust systems (like my Limited) so I only have to do it once. Either way, I don't object to the sound. If you want that super quiet OEM tone, my experience says aluminized steel is the right choice.


As for gauge, my Limited is all 16-gauge. Not sure what is on my Cadillac, but it's suitably beefy. I think the low-cost stuff is 18-gauge. You could probably call the manufacturers and see what they use. It may also be application-dependent. The header pipe closer to the engine might be heavier material than the tailpipe(s) simply because it has to be. Once exhaust hits the tailpipe, all the heat and energy is gone so the material is less critical. That's usually why you see exhaust systems rotting from the rear-forward. The lighter gauge stuff rots first, especially since it's cooler and more moisture tends to collect there.


This is not scientific just my experience. Your mileage may vary.



Edited by Matt Harwood (see edit history)
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I just measured 14-gauge on the tailpipe of the Super.  Classic Exhaust emailed back and said they use 16-gauge.

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I used Classic Exhaust on my '29 Cadillac, on Melanie's Chrysler, and they built the large stainless muffler on the Limited. I've always been pleased with their work and we've never had problems with fitment. Better yet, they're local to me (1.5 hours away) so I can always go pick up what I need without the shipping expense. Very small operation and they don't carry inventory, so if you want something from them, be sure to give them some lead time to get it built. I think my Limited muffler took about two weeks. Good guys.

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