Question for exhaust experts.

I wouldn't recommend coating your headers. Ceramic coating works great keeping underhood temps down, but the heat doesn't go away. It is bottled up inside the header and cooks the steel in the header more than the stock heat shields do. The best thing you can do for header life is to let them dissapate as much heat as possible, even at the sacrifice of higher under hood temps. In a perfect world, you could remove the stock heat shields. The problem with doing that is the components around the headers would suffer from the direct heat. A friend of mine put a set of aftermarket headers on his Berlinetta and went through three alternators before going back to stock headers. The aftermarkets had no shields and were cooking the alternator.
I would say the best way to combat the heat is to install a challenge grill (if you don't already have one), put a performance exhaust on (less backpressure, less heat), and finally ,if you are willing, take off the cats and put in test pipes. These three items will signifigantly reduce the heat your headers are exposed to and definitley prolong their life.

 

Colby I am in the process now of replacing the headers on a 355 that spent it's life with a Tubi, bypass pipes and a Challenge grill.

The headers have to have heat shields or everything else under the hood will perish. Go with a set of Tubi insulated headers.

 

Yes Brian that was my point, not remove the heat shields. Maybe I didn't convey my message well. As far as the bypass pipes, and challenge grill, I merely think it will prolong the inevitible header problems, not eliminate them. I wish I had a picture of the inside of that header we both dealt with on Dan's 355. Crazy what can happen to one of these headers. I am curious what your feelings are on the ceramic coating.

 

I would think that ceramic coating would be a good thing. It's true that the internal temps will be higher inside the exhaust headers, but the ceramic will see most of that heat instead of the thin OEM metal.

Likewise, the hotter internal exhaust is going to flow faster due to the physics of thermodynamics, essentially reducing back pressure some small amount (though the smaller internal diameter might negate that pressure advantage somewhat).

Ask Vern Cornell. He's coated his 355 Challenge headers for a some time now, and he's got the track miles to have some valid feedback.

For that matter, coat the outside of the headers too and ditch the factory shielding (not something to do if the outside isn't ceramic coated or thermotec wrapped, though).

 

Yes it would help! A big reason factory insulated/shielded headers go bad is they are insulated to keep the heat in the metal and when they get hot, the oxygen in the outer air attacks the stainless and breaks down the structure. If you insulate the "inside" assuming a thorough job, more of the heat will stay in the exhaust gases themselves. Even though the outer part of the tubing is not coated, it will still benefit because they will not be exposed to "as much" heat . A probable downside is your cats may suffer from the added temps.

When one buys aftermarket headers they always void the warranty when people use thermal wrap on them. This is the same reason.....the headers get hotter than normal with the wrap on them. But there is nothing to protect the "surface" of the pipes from the "oxygen" in the air. So idealy ceramic coating the inside and out is the ticket.

To give you and idea of why the metal breaks down when heated:

Imagine someone TIG welding without an inert gas shield.....the metal just gets contaminated by the oxygen in the ambient air. So the ceramic coating acts like an inert gas shield so when the metal gets hot, the oxygen cannot get to it !!

 

I didn't realize you meant the inside of the header. I suppose this would help as it will keep the heat away from the stainless walls of the tubing. I have to say, I have no experience with this concept and I am interested in the result if it is done.

 

I had the headers and the muffler system ceramic coated earlier this year; the inside and outside of each part were coated as they were dipped...I was under the understanding that this was normal?

However, the results were excelent. The temps around the CV joints (512 BBi) are much reduced, the temps at the rear above the mufflers are reduced to the point I have removed the 'aftermarket' heat sheild that someone had fitted, and the looks are infinitely better!

Lastly the sound has improoved...more of that 'monaco tunnel' howl as the rev's rise.

The work was carried out by Airborn Coatings in Oklahoma City. The service was excelent, and the cost was very reasonable. (405) 685 4433 I have no affiliation with the comapany.

Robert
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I had a set of ceramic coated headers on my TA. They were great. A good ceramic coater will do both inside and out of the pipe, which prevents heat transfer into the metal and into the engine compartment, and if done on both sides of the pipe it will prolong the life of the header. These guys will coat anything. Just send them the headers.

http://www.jet-hot.com/?gclid=CKbjsLLPoYkCFShCYwod-CiJVA

 

+1 Jet Hot'ed the heavily tracked 308's headers.

 

Darrell,
I think so poorly of the stock headers, that I doubt it will do anything to help them, they are so hopeless. But as you said, what have you to lose? So why not, give it a try, and keep us posted. As Rifledriver says, be sure to reinstall the heatsheilds. You are planning to coat both inside and outside, yes?

Dave

 

I will be doing the same in/out to set of 3.2 Tubi s/s headers in January as well based on this and other threads. Should be interesting.
Good luck and let us know!

 

Ceramic coating, like all refinishing, is all about preparation... I feel you couldn't be 100% sure of cleaning the inside a manifold well enough to be sure of it sticking properly... and if it comes off it'll go into your cats and cause problems there...

If you had some new un used ones it'd be worth a try maybe...

My 360C system is coated inside and out, and I don't use heatshields apart from one small one near the alternator.... but this is a race car...
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Go ahead and coat them. Ceramet does a decent job (ceramic mettallic paint). That is what the majority of coaters use. The best is plasma sprayed zirconia coatings. Much more expensive and, well, the white color puts some off. Your choice: form or function. Stay away from header wraps. Those are what cooks the headers causing metal fatigue and failure.

 

Does the zirconia coating stick well to poorly prepped surfaces, like the inside of a used header might be? I too thought about how bad little flakes of coating would be for your cats.

 

You know what would be cool? A solid ceramic manifold.

 

That's silly. That sort of rumor has been repeated too often. Thermotec header wrap is fine. I used it for 55,000 miles over ten years on the headers for a 1995 Corvette, and the exhaust headers still look like new today.

What the header wrap *won't* do is help 355 owners save their OEM headers from their expected failures.

Ceramic coating the interior (exterior too) walls of 355 OEM headers might save them, though.

 

Zirconia is sprayed melted (high heat) from a gun. You won't get coverage past the first bend in the tube. There really is no reason to do the internals and with zirconia its really not done.
http://www.swaintech.com/store.asp?pid=10969 and http://www.poeton.co.uk/coatings-motorsport.htm
http://www.poeton.co.uk/w1/a800.htm

 

I'm having a very hard time believing that ceramic coating the inside of the tubing is going to cause premature failure to the metal. Please explain the metalurgy that allows a colder metal to fail premature over a warmer non ceramic barrier stock pipe?

The whole reason to ceramic coat the inside and outside of the header/exhaust is for gain in HP but also longevity as well as cooler temperatures in the engine bay.

Ceramic coating is used in exhaust ports in the top of pistons as well as the combustion chambers for the same reason......ooops secret engine bldg techniques slipping away....

Now if you coated only the outside, yes the metal would fatigue in a matter of about 10 race hours.

Been there, done that....or am I smok'n crack?

d

 

That stuff was secret about 15 years ago. It's old and busted. This is the new hotness http://www.bekaert.com/bac/Products/Diamond-like%20coatings/Racing%20Engine%20Parts.htm

 

Interesting. In my experience in racing, as well as turboing many a Ferrari & Porsche I've seen the exact opposite. It did in fact cause quicker failure and I would thus have to raise my eyebrow. I build on average around 10-15 pro race engines per year and have so for quite some time now.

Insulation, thermotec does work and sometimes it has to be used in conjunction with ceramic coating or in use with even Inconel like we do in the Group C cars we run in historic venues now. IF you could put the thermotec inside as well as outside, I think it would be what the modern ceramics are doing at significant weight savings.

Coatings are not black majic anymore. Your pro engine builders don't like talking about it as it's giving away an edge as it's only recently a necessity to be competive....as in two race engine rules and the demands placed upon lighter and faster moving components.

d