I am thinking about adding true dual exhaust to my car, can anybody tell me what the differences between the aluminized and stainless steel?

Corvette Central only sells the aluminized and make it seem like the "best thing since sliced bread".

Mid America sells both, but the S.S. is $50 more.

The car is only a nice sunny day car, what is better? I want to buy once, and buy right.
Thanks in advance,
Alex

 

Stainless does not rust, more or less a one time buy, usually it is about double the price for SS as compared to aluminized.

 

Welding can be an issue with stainless. So can clamping if you go that route.

 

I read where stainless holds in more heat,a real problem for vette owners.If its only driven sometimes either way would be ok.Read more on what they have to say about alum. vs. ss.Both look good on your car and neither will show rust

 

Stainless can look ratty like ordinary steel and is used on most new cars. It is 409 series and while it doesn't rust it isn't also good looking.
Aluminized is just a coating over mild steel to prevent rust and give a better look.
409 stainless is also aluminized for looks.
Of the 2 stainless is more resistant to rust.
304 stainless is shiny.
Welding?? Everything will weld stainless, mild steel rod/mig welds fine, might rust in a while but some of the chromium and nickle leach out of the parent material when welding and help a little.
Stainless rod is expensive, stainless wire is very pricy as is the gas so welding with mild steel is an option.

 

Don't we want our exhausts to hold heat?? Why am I header wrapping?? How about coatings.
'Heat held in the exhaust is good, improves gas flow and keeps it off the floorboards.

 

also, when building a stainless exhaust figure in that it expands with heat more than mild steel so you want to make sure you have room for expansion. Stainless will also sound different from mild steel pipe.

 

Aluminized is not Aluminum, it's steel with an Aluminized coating for rust protection. It lasts a long time but not like S/S. As far as heat goes, you want to keep the heat in an exhaust pipe, it enhances flow.

I got s/s system (Dynomax) for my '82 from Mid-America it was the same price as the Aluminized one. I have it clamped and no problems.
There was a big difference in price in the mufflers, so I got the aluminized mufflers.

 

I have aluminize now for almost 4 years and it look like the first day they were installed, bright and shiny. I f you have them custom made aluminize is easier to bend.

 

I went with the Stainless exhaust from Allens---love it--great fit--great flowing--added the Dynomax Super Turbo's at the same time

SEMPER FI--1970 Dave

 

I have aluminized pipes and they look like they did when they were put on 7 years ago. I am going to a 3 in. system and it will be aluminized too no point is spending extra cash on SS if it is sunny day driver in my opinion

 

Not sure what year GM started doing it, but the factory pipes on my '81 were SS, 409 I think. And after 24 years, they were still in excellent condition. I just took them off recently to install true duals, from Mid-America, and yes, I got the stainless.

Some SS pipes on some vehicles make more noise, the popping and cracking of expansion/contraction, but the pipes on my Vette never had that problem.

I think that all aluminized pipes are not the same, but vary in quality. I have had aluminized pipes on other vehicles where the aluminum coating burned or wore off in spots, leading to rust and rapid failure thereafter. On other vehicles, the aluminized pipes are as good as new after a decade. It's got to be the quality of the coating, either in material or application, or both.

For the small extra cost of SS, and no significant downside, it was an easy choice for me.

 

It's important to distinguish between types of stainless as some have done. Briefly:
1. aluminized carbon steel is a diffusion coating deposited at high temp, not originally meant to deal with aqueous corrosion which is what an exhaust is exposed to, but does a pretty good job in extending life. Will eventually fail by local pitting but may be acceptable for infrequent use.
2. 304 stainless is expensive and most corrosion resistant mat'l used- also most expensive. Will not corrode and will retain silvery luster and will last more than life of car. But- has high coefficient of thermal expansion and more susceptible to cracking if constrained. Can identify since it's nonmagnetic.
3. 409 SS is the material used in OEM SS exhausts and, in my opinion, is the optimum choice- intermediate cost, will not corrode but will discolour, will last life of car, same coefficient of thermal expansion as carbon steel- therefore no noise or cracking issues. Is magnetic.

 

Stainless for me as well. It does expand more than steel exhausts, but the system on my Vette (and Gator81's ) is supported by the manifold/headers & by flexible mounts on the mufflers. There may also be flexible mounts supporting it from an x-member. With all the flexible mounts, and the amount of bends in the system, there is plenty of room for it to move about due to the expansion. Solidly mounting it throughout its length is asking for it to crack (same applies to steel systems).
Aluminised systems can be great, but a lot depends on the manufacturer & whoever fits it. My daily driver eats aluminised systems (the latest has just blown a hole). The places it usually goes at are on the slip joints where it gets surface damage when the "highly skilled technicians" at exhaust centers bash it into place. They can also cause problems if the vehicle is used for a lot of short journeys as condensation build up inside can rot it through (another problem with my DD - an exhaust system that looks perfect on the outside has serious corrosion at certain points on the inside, usually at the bends). A good quality aluminised system can last for years but the trouble is that you just don't know if it's a good quality one or not. Or if there's any exposed steel inside to rot out.
For many years a lot of mates have used custom made st/st exhausts on their bikes which are solidly bolted to the engine & frame. There's never been any problems with cracking due to expansion. Granted, it's nothing like the length of a car system, but if about 3' of pipe can survive being bolted firmly in place then a car system with flexible mounts shouldn't have a problem.
In '79 my Dad bought one of the 1st Saab 900 turbos in the country. He then fitted, with factory involvement, a water booster & Saab engineers set it up & increased boost pressure. They told him not to use the standard system but to get a stainless system fitted as the standard (aluminised) system wouldn't last very long. I remember it clearly because the exhaust system cost the same as the fitted & setup water injection system! If stainless systems have problems then I don't think Saab would recommend one for use on a customers car that they were using as a testbed/demo of their performance enhancements (that Saab still blows the socks off my Vette, in '79 it was awesome It still has the same st/st system on it, even after a "mechanic" raised the car on a hoist placed under the exhaust).
There are 3 problems with stainless systems. One is the initial outlay, another is that stainless goes a grim straw color when heated by exhaust gas & the last, most important(!), is that the sound quality isn't as good as steel systems. It's more "tinny". I was worried about the sound when I first got my MA system but it's fine (although not as deep in tone as one's running steel pipes). It's also more brittle than steel, but if it's not under any stress, & no part is repeatedly bending up & down (like an unsupported muffler) then it's not an issue (I can remember the early 70's when the "experts" were saying that mass produced fibreglass cars were likely to disintegrate around you because it wasn't as flexible as steel. Can't think what type of car they had in mind? Reliant Robins?).
I think it's a personal choice (like DOT5 silicon fluid ). Some people like them, others hate them. What I know for a fact is that my wife bought an MGB about 10 years ago that had recently been fitted with a new & expensive aluminised exhaust system. After 2 years it had several patches on it (exhaust bandage, beer cans & hose clips) & when it rotted clean through & fell off one night it was the last straw. I threw it all away, got the cheapest st/st system I could find and fitted it. I've not had to touch it since & it's been decked out frequently on speed humps, on kerbs & in fields, bathed in road salt, backed into walls (for these reasons she's not allowed to drive the Vette ) & is very lucky if it gets used in the dry (it's a bad weather vehicle).
For me the choice between aluminised or st/st comes down to just the cost. The Vette is worth spending the money on, the daily driver is just going to get another beer can & a couple of hose clamps Just mount a st/st system so that it's not under any stress (ie. don't force it into position & hold it in place by bolting it there) & it'll be OK.

 

Just go to home depot and get some Flexible Dryer Exhaust tubing. Cheap, Easy and all you need is some duct tape to install it.

 

No it won't it'll turn straw color quickly, and it will do so immediately when welding, can be removed by etching, polishing or grinding but why would you want to, I like the looks of heated stainless...but it does not retain the luster.

As for tinny sound, I found it to sound a lot deeper than the steel pipes, not tinny at all..just different. I like it better than the mild steel pipes' sound. Slap on some absorption dampers. Tinny sound is caused by using thin pipes (cheapo) and cheapo headers, my exhaust pipes are a good 2mm wall thickness and they don't sound tinny at all...

 

I have had 304 SS pipes and mufflers on my car 18 years. They are bright and shiney as you want them to be as they can be polished to a brite finish. I have not had a problem with the system. 75 Hot One has given you good info. Chuck

 

This is what I mean with the discoloring, that's from welding


You can polish it off but I don't really mind the coloring. However, the exhaust system will turn that color if it getts hot enough, could be that in the back it stays nice & shiney but my downpipes are that same color, the stuff on my truck is also colored like that from the headers to about half way back

 

I have the Dynomax Super Turbo's on my 1980 and they still look good and the price was excellent. I have seen some of the stainless steel mufflers and I know they wont rust, but for the type of driving I do, the Dynomax Super Turbo's will be on for a long time.

 

I had a set of steel headers aluminized several years ago. The headers were first sand blasted to get down to clean bare metal. The aluminization process involved a gun that used an electric arc to melt a piece of aluminum feed stock and a high pressure stream of an inert gas (argon?). The high pressure gas "blew" the aluminum plasma onto the steel. The headers had a cast aluminum look to them. I was told that it was possible to polish the aluminum to make it shiny (I never did.) When I spilled a fluid on the headers and stained them I was able to remove the stain with fine sandpaper.

The process seemed durable. I had one piece of aluminum flake off to expose the metal underneath.I had to sand off some of the aluminum at the collector edge to get it to slip into the sidepipe. This create a later thin ring of rust.

This aluminization process didn't add any protection to the inside of the mufflers.

Also, I was told that it would not be possible/very difficult to weld the steel after aluminization. I was told that aluminum atoms were driven into the steel and this would contaminate welds.

This aluminization process was very cheap and good value for the money. Stainless steel or the ceramic coatings (jet-hot) are much better but you're going to spending much more money. ...Actually, I'm not a guy that tries to save every last dollar on my cars. But really, the really cheap aluminized plasma spray was a very acceptable process.