Differences in stainless steel mufflers
About 12 years ago, I replaced the pipes and mufflers on my '68 convertible driver. I used stainless pipes and aluminized mufflers. Lately, I have noticed a change in sound. After checking, I found the passenger side muffler was all rusted out. I'll bet I have less than 3000 miles on that muffler. I try to make my drives long enough to completely warm up and dry out the exhaust system, but that muffler is shot. Since the stainless pipes are still like new, I am considering replacing the aluminized mufflers with stainless ones. A quick check of the internet shows a great range in prices for stainless mufflers. I see mufflers made of 409S stainless for $82.99 and others of 304 stainless for $450.00! Any metallurgists or other scientists on here that can tell me the difference? This car is a driver and will never be judged, so function followed by price are what are important.
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Re: Differences in stainless steel mufflers
Dennis,
The 304 has higher nickel, chromium content. Better against rust. The moisture from short trips is the devil eating up your mufflers. Keep in mind you get what you pay for (or at least low cost is generally lesser quality). -
Re: Differences in stainless steel mufflers
Dennis------
Get rid of the heat riser and your right side muffler will be "immortal".
As far as stainless steel exhaust goes, I like only 304 or 316. Those are the best and most practical alloys for exhaust system purposes. Personally, while I LOVE stainless, the only exhaust system components I'd be interested in are 304 or 316.In Appreciation of John HinckleyComment
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Re: Differences in stainless steel mufflers
Dennis I put a new passenger side muffler on my 1968 L79 on January 27,1990 . I used a Walker guaranteed for life muffler that I bought at my local auto parts store. I have not seen or heard any problems, no rust out. The heat riser valve was wired open before I put the muffler and new pipes on. Pretty sure the pipes were Walkers, if not they were bought at my local Chevy dealer. I bought two Walker mufflers but did not install the drivers side because the drivers side was not rusted out and I really liked the sound the muffler made. I did install the second Walker guaranteed for life muffler on the drivers side on September 3,1997.Comment
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Re: Differences in stainless steel mufflers
Dennis
Type 409 series is a "straight-chrome" stainless, nominal 11% Cr & balance iron with no nickel, & only traces of other elements -- usually Ti &/or Nb. It is commonly known as 'muffler steel' in industry & really came into high tonnage with the advent of catalytic converters in the 70's. It is a magnetic stainless grade & is also widely used in the exhaust stacks of gas-turbine electric power plants (EGT's up to ~1000F). It is normally a sheet or plate product, as it is more difficult to weld and shape than the much more expensive 300 series stainless grades. (300's are all non-magnetic & are variations of 304, nominally 18Cr-8Ni, balance iron). I would not hesitate to use 409 if the welds on the mufflers your considering are sound & exhibit no corrosion.Comment
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Re: Differences in stainless steel mufflers
Thank you gentlemen for the excellent replies. When I replaced the exhaust system, I made sure the heat riser was free and worked like it should. In retrospect, I should have fixed it an open position, given the driving conditions I experience. I will be changing the heat riser and will probably go with the cheaper 409S mufflers after reading Jeff's informative post. Unfortunatley, I probably won't be around long enough to post an evaluation of my actions.Comment
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Re: Differences in stainless steel mufflers
Dennis,
You may experience welding problems welding 409 to 304. Try a 300 series welding wire.Comment
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Re: Differences in stainless steel mufflers
Hi Dennis, You may be experiencing galvanic corrosion to some extent. The carbon steel mufflers are anodic to the stainless steel pipes. Kind Regards, PeteComment
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