Stainless versus Mild Steel Exhausts

[Merv and Sharon]

I am planning to order my exhaust system for the 302 (US Mustang - sourced) that I have coming this week. Wanted get a few ideas on options, if possible. I understand the potential rust issue with a car that is driven infrequently, but what are the advantages/values of stainless over mild steel exhaust systems (I will have ceramic coating both sides anyway)? There is a considerable cost difference.

Also any recommendations re types of catalysts would be appreciated. Do I need to use the standard ones (replacing the existing ones - if they are there) for the Mustang EFI motor for registration?

Other thoughts also welcomed!

Thanks,

Merv

[cameron02]

The ceramic coating inside and out will prevent rust, I even had my mufflers done. Personally I cant see any reason for haveing stainless if you are going to coat it.

[Merv and Sharon]

Interesting Cameron. I am wondering how long others have found their systems last for, if made in mild steel and then coated with ceramic? Stainless does seem a 'luxury' to me, but I may be wrong there.

Merv

[400TT]

Merv, I have a 12 year old Cobra here with it's original exhaust system. It was only painted with high temp paint. No problems I can see with the exhaust and corrosion.

The headers were ceramic coated though and they are also still going strong.

Same deal with our last Cobra. It's also still going strong with just a high temp paint and is 11 years old now.

So ceramic coating the entire system will be more than adequate.

In my experience stainless systems sound different to mild steel systems. Although polished stainless headers look fantastic. But if you are looking for lower engine bay temps, then ceramic is the way to go.

The only thing I have seen that deteriates exhausts quickly is that heat wrap.

[CHANMADD]

I have 20 year old Mild steel headers and sidepipes and have periodically repainted them and I think twice I have had them sandblasted and then repainted them myself with Aerosol Ceramic paint. No problems at all, and if they do get dirty or whatever I just whip out the Aerosol can!!!

[Merv and Sharon]

Sounding good!

[400TT]

I think the killer when it comes to exhaust moisture and corrosion is if you don't fully heat the exhaust system when you run the car.

So if you are just starting up the Cobra to just give the engine a run, make sure you run it long enough to burn off all the moisture from the exhaust and get a resonable amount of heat into it.

Or just make sure you drive it often enough, hard enough and long enough to get some good temps into it.

[Merv and Sharon]

OK I think I am getting the picture. I felt that the stainless was a luxury and at this stage of life I want nothing that will outlast me! Mild steel with ceramic inside and out it is. I will also take up his suggestion re the headers - larger flanges - so that when I fit the alloy heads and moderate cam later it can be accommodated.

Merv

[cameron02]

Make sure you have test fitted your headers and exhaust before getting them coated. If you have to do any welding on the system it will wreck the coating in that area. (I learnt the hard way)

[Dimi]

Given that in most cases the exhaust system is custom made and is generally not cheap to have made I personally only want to pay once and feel satisfied that it wont rust and last.

To have a system made in mild steel and then find down the track it needs to be made again due to rust does not thrill me in the least.

I need to know it will only have to be made once and then I can forget about it as one less thing to think about.

Stainless is the only way for a custom system.

Dimi

[Outwest34au]

My peference would be mild steel for the headers if you are going to handmake them or if they are long and dangly going to collectors for side pipes. Less prone to cracking under high heat but all that crack risk is dependant on how tight the bends are. As for the integrity of ceramic I dunno, looks pretty, sounds perfect in theory. But if I can't afford it on the day I wouldn't be grumbling about VHT pressure packs at all.
The average mums car that just does short runs and never gets "REALLY' warmed up would definitely see a longer life in the horizontal underbody system if stainless. And by warmed up, I'm not talking racing, just allowing a long enough time to get full heat soak to the exhaust. Mufflers towards the rear will obviously gather more condensation over time than forward mounted due to the time it takes to heat soak. Heat soak is different than just thinking you have ?x? amount of degrees C blowing thru it. Exhausts inherently are not de humidifiers.
If I had one tip to offer for an "infrequently" driven car, hmmm, drill a 1/16 or better 1/8the inch hole at the low point of the muffler. Might sound silly, but look under the rear resonator on most bog stock factory family cars and you'll find that hole. Then observe the neighbours car and you'll notice the odd drip.

My 2 cents worth, which rounds down to zero nowadays we know.
Cheers

[T.L.]

Hi guys,

I use to work in the exhaust industry, and I can say that if you start your car up and run it for less than 5 minutes, all your doing is gathering moisture in the rear can of a complete exhaust system. (as was said above)
Given nowadays that most new systems on cars are full stainless, and tend to last >7 years, stainless is the better for this application.

Now given what this website is all about, and when we do get into the cars we tend to either give a quick blast on the throttle to impress our mates who are over for a beer and barbie, the moitsure is blown out of the system. I had a mild steel set of extractor on my old VY SS that did the trick and an alumised steel exhaust system for the rest of it. I had the car 5 years, and never had a problem with rusting, as it was given a caning most of the time, as it sounded great , and went to 6250rpm as quick as.

Given the cost factor, (Stainless steel is usually 2x the price as it has a higher wear factor on the tooling used to bend the pipes, but will last 3x as long on your wifes car), I will be going for a normal alumised steel exhaust system on the car, with mild steel extractors. I have not got as far as worrying about coating/painting yet.

You can put a small hole in the lowest point of a muffler, as Walker do on some of their mufflers, but all your doing is breaking the coating over the mild steel and giving rust a nice place to start. Usually the muffler will need to be replaced, and very rarely a set of extractors unless you hit something.

Stainless steel extractors tend to crack more than mild steel extractors, due to the combination of heat and the weight of the system flexing at some point.

If all else fails, just drive up a long hill towing a caravan, then your system will get hot the full length of the exhaust system and will evapourate any moisture, or if that sounds too volvoish with tweed hatish, just rev the crap out of it when you can.

Hope this helps.

[Merv and Sharon]

Actually the difference between stainless and mild steel is not so great in the quotes I am getting - about $4500 from headers to tailpipe (inc new cats).

Merv

[sambo]

That seems a little on the high side Merv. $1400 for Warwicks custom headers (if you had a Chev), surely the rest of the system isn't worth another $3100?

[Bryan Wilson]

My headers are mild steel and jet hot coated. The jet hot burned off and the headers rusted through where the four pipes come together. I had them welded and repaired and they are now high temp painted silver and they look a lot better. If they get dirty another coat of paint has things looking good again.
My external side pipes were 100% stainless baffled pipes that were extremely hot and sounded tinny.
the external pipes are now mild steel hot dogs with stainless outers and a 1/4" air gap between the hot dog and the outer stainless skin. These pipes have a deep rumbling growl and sound great but don't get hot enough to burn skin

Cheers,
Bryan

[Merv and Sharon]

Thanks - will check to see if Warwick has any custom headers for the 302. One quote for a coated mild steel system (no side pipes) was about $3000.

Merv

[sambo]

At that price I think Mike Murphy should open up his production line again!!

[Barker]

Merv my headers are steel HPC coated and the ehxaust is stainless polished keep a good coat of polish on these and no rust issues. I live on the coast and salt is an issue( you saw my car ad DBN04 's place ) and elbow greese is the key.
Sounds like you have made up your mind but it should be there forever.

Happy Motoring.

JB

Barker

[Merv and Sharon]

Thanks - yes I remember seeing your cars. Great ones. I am being pursuaded to go the way you suggest now. Did you get yours made at the Sunshine Coast?

Merv