Header color question

Here is a closer view of the driver side where rust is probably the worst.

The ceramic coater will definitely blast all the rust off the headers, but the real question will be what are they going to look like after surface is prepped, and if there are any thru holes or thin spots. They might look like ceramic coated pits. They are not going to smooth the metal, just remove the rust.

Also, if you are going to coat the headers, get the pipes down stream of the headers coated as well. They can mask off the mufflers if they are welded to the pipes.

Thanks Dave, I agree, to ceramic coat these now may be too late, not that the rust is bad, but just that it wont look smooth like coating a brand new metal.

Maybe I should just consider replacement with some ceramic coated ones or maybe repainting with some VHT 2000 degree paint.

before sending them for coating look inside the outlets . this one is restricted by half with the misalignment of the two pieces that create the extension and the flange.

view from inside .... the outlet is only 1 7/8'' tubing. this set of headers was converted to 2 1/2'' collectors and tailpipes. [see rocky's post in specific cars]. his drivers side showed evidence in the merge area of running hotter[ due to restriction \

Hall big bore headers were not painted but rather "aluminized" I have had a set for nearly 25 years and there is no hint of peeling or nothing like what yours show. Something is amiss here.

Rocky's headers were aluminized also.

Wade - They look just like the picture in the merge area, perhaps that created some of the issue.
PPat - I would agree that something is amiss here. The best that I can surmise is that the PO had purchased a pair of Hall Big Bores as I have that receipt, but possibly only installed the passenger side and the driver side may indeed be something else. At this point they are off and I am contemplating options. Any suggestions?

the merge portion of these headers is well done for the price the extension and flange are the issue. if you go in to the header with a grinder most of the restrictions can be removed. if original is not a problem, remove the extension, and tail pipe to muffler and replace with 2 1/4'' or 2 1/2'' . original exhaust on a 351c 4v mustang was 2 1/2 to muffler 2 1/4 tailpipe for a reference....Rocky's engine is @5oo+ hp 17/8'' pipe is way to small.

inside view ; take a few minutes an grind some of the lumps in the merge area. as for finish jet hot is great w several finishes [ i like the black ;burnt skin doesn't show on it]it is done insde an out. also, some powder coat shops have a coating good to 1200 degrees

These are Halls big bore headers. If you are going to do work to them, why not put real collectors on them so they work like they are supposed to do?

The ceramic coating is for functional reasons. It's a secondary benefit that they look so nice done.

The coating is fairly thick and I was concerned that mine would show all of the pits in the tubes.

It doesn't. the tubes look a lot like mill finish stainless does and you see NO pitting in them at all.

I was also concerned that the interior of the tubes would have too much petrolium residue to hold the coating.

The people who did nine, Central Connecticut Coatings, said that they had a special soaking tank for them that removed everything.

There isn't even one fish-eye on mine.

I purchased Wilkinsons new stainless headers and mufflers for my car. The dyno specs for them are darn near open header horsepower. The paint he uses will only last till you start the car.
But I looked at several sources for ceramic coatings (for the mufflers)and they all told me they used burn off ovens to prep. This method will burn off anything that is on the base metal. But to me to expose a stainless muffler with polished tips to those sorts of temps will ruin the tips and burn out all the packing in the mufflers.

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Originally posted by OSOFAST:
I purchased Wilkinsons new stainless headers and mufflers for my car. The dyno specs for them are darn near open header horsepower. The paint he uses will only last till you start the car.
But I looked at several sources for ceramic coatings (for the mufflers)and they all told me they used burn off ovens to prep. This method will burn off anything that is on the base metal. But to me to expose a stainless muffler with polished tips to those sorts of temps will ruin the tips and burn out all the packing in the mufflers.

I don't understand why you are talking about painting or coating a stainless exhaust system.

There are two kinds of stainless that are in general usage for exhaust systems.

One is the 409 which is what is now used by Borla and most of the new car manufacturers.

It develops a coating of rust on the surface and is not a cosmetic grade. That one could be coated for appearance reasons, yes.

The other is the 304 and similar grade which in its natural state has a dull mill finish to it but if polished looks a lot like chrome.

That's what Wilkinson used, 304, and what most are referring to when they say they have a stainless exhaust system. It needs no ceramic coating.


Ceramic coating on exhausts is useful on regular aluminumized steel or mild steel used on exhausts and headers.

They put it on both the exterior and interior surfaces. There is some documentation, done by that group of coaters, that shows headers flow more when the insides are coated. Numbers for something like that were ridiculously high I think, somewhere in the 3 to 5% gain in flow I think is what I remember the claim to be?

I have it on my 180 headers and really eliminates the necessity for using 304 stainless at all on the exhaust system.

The manufacturers, at least mine, tumble the headers when they are done to buff them. When done they resemble stainless that is somewhere in between mill finish and polished.



You normally don't ceramic coat 304 stainless. Central Connecticut Coatings did my headers. They did tell me that they can ceramic coat 304 stainless, but why would you want to? The point of using it was to have a system that needs no maintenance. Not necessarily for more glitz but that's kind of unavoidable result?

It is nasty to bend smoothly without kinking it and is not the simplest materials to weld up.

What I don't like about 304 stainless is it is going to blue from the heat of operation of the engine just like chromed systems do. It will also eventually split or crack through the mandrel bends from the normal use of the engine and the heat cycles the engine puts it through. The term is work harden. Regular mild steel exhaust tubing does not, at least not to that extent. That makes coated mild steel better than 304 stainless and in my opinion makes 304 stainless obsolete, with the exception of use for the mufflers, which do not get as hot as the headers do in operation.

My mufflers are 100% polished 304 stainless and have not blued at all yet.


Each type of muffler is dealt with differently by the coater but the key to the ceramic coating is that whatever it is being coated has to be able to stand being cooked to about 750 degrees Fahrenheit to cure the ceramic coating.

I don't think that effects the muffler packing at all. Some mufflers don't use packings at all, just a series of chambers internally to reduce noise.

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There are two kinds of stainless that are in general usage for exhaust systems. One is the 409 which is what is now used by Borla and most of the new car manufacturers.

400 series are martensitic steels whereas 300 series are austenitic. “Stainless” is a generalism in reference to resistance to oxidation but generally speaking 400 series alloys are not true stainless steels. They most frequently are used because they are more workable and able to be precipitation hardened after forming to increase mechanical properties. These gains can not typically be preserved at exhaust gas temperatures. They can also be more economical than 300 series alloys. 300 series contain more chromium and nickel which provide better corrosion resistance but cost more.

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What I don't like about 304 stainless is it is going to blue from the heat of operation of the engine just like chromed systems do.

304 still oxidizes. It just doesn’t look like rust. Tan is the more usual discoloration for 304.

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It will also eventually split or crack through the mandrel bends from the normal use of the engine and the heat cycles the engine puts it through. The term is work harden. Regular mild steel exhaust tubing does not. That makes it better than 304 stainless and in my opinion makes 304 stainless obsolete, with the exception of use for the mufflers, which do not get as hot as the headers do in operation.

I don’t think I can agree with any of that. If we’re talking a normally aspirated street car, a properly designed and fabricated 304 system would be a lifelong system. The only cracking on such an install would come from improper welding by either no shield/purge gas or use of improper filler rod. The only other mode of failure would be from lack of strain relief due to thermally induced growth and stresses. The exhaust temperature cycling tends relieve stresses induced in forming, even in the austenitic 300 series.

Mild/carbon steel exhaust systems, coated or not, are not a superior material to 304 and it’s mode of failure in an exhaust system is usually due to the operating temperature of the system causing carbon to precipitate making it more susceptible to accelerated corrosion. This is especially true in proximity to welds. Exhaust temperatures seriously degrade the mechanical properties of mild/carbon steels and they wouldn’t be used even in moderately stressed applications at these temperatures, but they are very economical, lightly stressed in an exhaust system, practical, and good enough for most folks given the application.

For what it’s worth, a street car isn’t much of a challenge to either material because the exhaust gas temperatures and duration of exposure are nothing compared to the racing environment. The far more difficult exhaust test is turbo installations which need to preserve the heat/velocity of the exhaust gas to be efficient and effective. These systems will operate at much higher temperatures on the street and especially at the track. Great care is spent in the design of high performance turbo systems for strain relief and supporting components such as the turbines because these systems operate at temperatures much closer to those that seriously reduce the mechanical properties of even stainless steels, and they’re made from thin walled material to be as light as possible. FWIW, the choice of materials for pros is typically 321 stainless, other high nickel alloys, or even Titanium.

If you are coating carbon steel because you expect big temperature reductions, you’ll likely be disappointed. Most of that is marketing BS and is the thermal equivalent of bench racing. The popular coatings just aren’t thick enough to have the claimed affects. There are thicker ceramic coatings that are much more effective but they aren’t pretty like Jet Hot and the other popular cosmetic coatings and they are not easily applied. The primary benefit of commonly available ceramic coatings is cosmetic and durability/life due to it limiting the ability of the carbon steel to be exposed to the reducing environment when it is most vulnerable at temperature and these coatings are actually very good at both. In a street car environment you really do get a big increase in service life and they look good to boot. They still won’t outlast a 300 series stainless system.

A 300 series stainless system will typically run cooler than a mild steel system because it is a poorer conductor than mild steel and all heat must conduct through the header walls before it can be transferred to the engine compartment. Initially, heat is transferred primarily by convection from the high velocity exhaust gas, then conducted through the header wall. Once conducted, heat is imparted to the engine compartment by convection and radiation. The best hope for the commercial coatings reducing temperature is reducing radiative heat transfer. Ironically, people like to have the ceramic coatings polished which make them a better emitter of radiative heat transfer.

And BTW, engine compartment temperatures are a strong function of exhaust system surface area and 180s have way more surface area than the typical 4:1 system.

-My 2 cents.
K

Gotta agree with Kelly. Stainless has a heat conductivity of ca. 14-16 while mild steel has a conductivity of around 22-31. So stainless exhausts naturally run a little cooler as well as looking pretty more-or-less forever. That's why stainless water tubes will leave your Pantera interior a bit cooler. And it brazes beautifully if you're not up to TIG-welding repairs.

Off-subjectnote: wanna-be bikers with stainless exhausts can buy a product that artificially 'blues' the headers in a few areas so it looks like they've really been pushing the machine. Blue headers means power to some!

My ceramic coated headers will far outlive me. I don't need a system to outlive me, my kids and their kids. Let them build their own system!

Yea. I got a couple of cracks through the mandrel bends on the SS headers Jay Bittle built for me 30 years ago. I was putting my A3 heads on a 351c in my 68.

That set up is out of there 10-12 years already.

I can weld mild steel. SS is a b itch for me to work with. I'm not NASA. Either you need to be or the guy who is building those stainless headers for you does.

Not only that, I have to go back and look up those terms Kelly. If I say hi, do you need to pull out your calculator, run an equation, then say probably? LOL!

The headers on the Holman-Moody Mark IV "continuation: GT40s are all stainless. Tig-welded I presume, and have a strange low level rust color to them.

Me no likey. Look like do-do ka-ka to me.

For a million a car, I'd definitely not be happy with that situation.

Coat me. It does everything I want. No low level rusty surfaces to stress over.

Didn't notice my stainless water pipes were cooler to the touch, or do mean cooler looking BW?

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Stainless has a heat conductivity of ca. 14-16 while mild steel has a conductivity of around 22-31. So stainless exhausts naturally run a little cooler

Can't necessarily agree with that statement. I've found that the stainless tri-y headers on my 66 GT Mustang seem to get a LOT hotter (although I didn't verify with an IR temp gun) and retain more heat longer than the mild steel tri-y's they replaced. With the mild steel tri-y headers, I could work on the engine 20-30 minutes after shut down without burning myself if I touched a header. The stainless tri-y's will burn you 1-2 hours after shut down. Just my experience. YMMV.

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Not only that, I have to go back and look up those terms Kelly. If I say hi, do you need to pull out your calculator, run an equation, then say probably? LOL!

Nahh. Don’t need a calculator to know stainless has lower thermal conductivity and better high temperature mechanical properties than mild steel. No offense Doug but while what’s better may well be a matter of opinion and tradeoffs, material properties are not.

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I can weld mild steel. SS is a bitch for me to work with. I'm not NASA. Either you need to be or the guy who is building those stainless headers for you does.

It’s a fair point. I don’t think TIG is rocket science but agree that it is much more common to find a MIG in a garage. If the welding isn’t an obstacle for you, surprisingly, I found there was little to no net difference in cost between 304 and mild steel construction for the headers I built because by the time I paid for freight both ways and for coating, it was about the same. I spent more on mufflers but that was a choice to buy light repackable mufs.

Best,
K

No offense taken. What I think, just me, is that the discoloration of stainless to me is severe enough that I would want to have them ceramic coated to maintain a consistant finish. That's all I ever wanted on headers to begin with.

If I am going to ceramic coat headers then why build them out of 304 stainless anyway at additional expense, then coat them?

Build them out of steel tube, then coat them.

The heat transfer for me is not any kind of an issue at all.

However I look at it. My $800 Hall headers are 4 times better than anyone elses $3,200 set, no matter what they are made out of.

They are just headers.


On the term "better", you reminded me of an "estimate" that I did for replacement windows for an "engineer". You probably know him Kelly?

He was pricing my wood "Andersen" windows vs vinyl replacement windows.

He got annoyed with me because I represented the Andersen's as "much BETTER". He snapped at me, "if we bury both in the ground, which will last longer?", and demanded an answer.

My answer was, "first of all, neither is going to get buried on this job, secondly, the vinyl are so poorly constructed, they will never last long enough to rot".

So it really depends on the application of the term "better".

We might also need to get into defining the term, yes or no, up or down, and pretty and ugly as well?

Remember the immortal works of Fred Sanford that "beauty is only skin deep...but ugly is all the way to the bone!"