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Discussion Starter #1 (Edited)
One of my favorite threads - the Demon - has our hero lately wrapping then unwrapping his as yet unused and ceramic coated headers.

The issues and discussion start here: http://www.alfabb.com/bb/forums/547333-post903.html

So I would like to start a thread to examine all the options for heat control of headers, pro and cons of various treatments, that sort of thing. I think the Engine Rebuilding forum is the correct venue for that, no?

Here is what I think I know, (means may all be wrong :D):

Headers put out a lot of heat. In street cars this can cause collateral damage to things like master cylinders. They are pretty, and increase performance, but can also be a PITA. What to do?

Ceramic coating: High tech. Not cheap. Reduces heat output, but how much? May only be done to brand new headers.

Wrapping: Labor intensive. Cheap? Reduces heat output, but how much? Changes pretty headers into something else. Causes irreparable harm to coated headers. Also causes harm to regular headers, but may be OK with hi-temp silicone to repel water?

Chrome Plating: Looks cool (sometimes). Reduces heat output???

Well, that is about it. I am looking forward to seeing what you folks have to add to the body of knowledge. My big question at present is this: If wrapping can be made to work so that it is not unreasonably destructive of the headers, how does it's heat reduction functionality compare with that of ceramic coating? Who does the better job, looks not withstanding?

Or has some wizard come up with a way to do both that does not destroy the headers? That would be best, I think. I am all ears.

Regards,
 

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heat and headers....good topic

ive never seen a set of wraped headers that got "street use" more than track use that didnt rot themselves to death

chroming from my understanding doesnt really do much but make the heat bounce off more

imo best bet is getting air flow across them as much as posible and shrouding everything you can that needs it
 

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how about stainless headers? I've heard these retain heat more by themselves, and surely these wouldn't rot away if wrapped?
 

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Discussion Starter #4
Does anyone have experience with wrapping using the hi-temp silicone spray? Does it prevent rot?
 

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wrapping cast iron or mild iron headers will lead to massive corosion and heat cracks ...SS headers not need wrap.. SSteel radiate heat 200% less than mild steel ;) wrapped ordinary SS(304L) due to very high temp will cause intergranular corossion :D internal ceramic coating sound good but i have not expirience...
 

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Well, as shown clearly here in the in the Demon-thread (http://www.alfabb.com/bb/forums/engine-conversions/31782-one-demon-possessed-91-s4-62.html#post561586), the pictures of the ceramic-coated, mild-steel V6 headers show the dramatic, short-term deterioration of just one section of a header that was wrapped!

The owner was trying to protect another component that ran close to the one primary on the left of his GTV6 and it turned out to be a very bad idea. The section of header that was wrapped actually swelled - like it was snake-bitten or something - and developed a blister and eventually a crack in the center of the wrapped area!

Upon talking to the manufacturer/supplier of the ceramic coating, I was informed that it is a VERY ad idea to use the two methods in conjunction! He further stated that with header-wrap, the heat is already IN the header and that you are applying a band-aid - if you will.

They are of the opinion that the ceramic coating inside and out (rated to 2,000 degrees), is much more effective at retaining heat INSIDE the header - thereby accelerating the spent gasses through the exhaust system and increasing performance! The additional benefit (here again in theory), is that you reduce the overall engine-bay temperatures - and with it - induction temperatures ad thereby further increasing performance! The story also goes that the reduced radiant heat also helps protect other thins in the area such as overflow tans from yellowing as fast etc.

I like it because it looks nice and on a mild-steel header, it takes longer for them to start looking like kaka.

Bottom line though - using the two methods in conjunction is a very bad idea!
 

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I had stock manifolds ceramic coated and then wrapped them. This worked well and resulted in a 3F-5F drop in intake air temps (my supercharged car had an Nordskog intake air temp gauge). The car never had any issues with the coating and wrapping, but that was with stock manifolds. I am pretty sure those manifolds are still on the car today, it´s owned by another member of this forum.

With headers, I don´t really now, but I figure stanless steel headers are the way to go, I might or might not coat them, but I probably wouldn´t wrap them.

Greg Gordon
hiperformancestore.com
 

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If you got a lot of spare change go Inconel - it is commonly used in Formula 1 and WRC, as well as some high power turbo applications. Also see:
Inconel_article
Heat shields may also be an alternative to wrapping - Alfa used to do that on some cars that came equipped w/headers from the factory. For instance, an 1/8" thick aluminum plate will often suffice for cars that have carb boiling problems - not common in Alfas, as they have crossflow heads; there also are some proprietary heat shielding materials available.
 

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OK, this is an area that I have some massive practical experience in. GMC Motorhomes with Olds 455's and headers produce massive amounts of heat in a very enclosed engine compartment that sits right under your feet and butt when you drive them.

In my opinion and proved with actual temp measurements the only ceramic coating worth using is from Swain Technologies. The Jett Hott, and the others are no more than posers when it comes to heat. They look pretty, and have a minuscule amount of ceramic in them and do a poor to nonexistent job at heat control.

With Thorley TriY headers and a Jett Hott ceramic coating my engine compartment ran in the 200 to 275 F range and when I pulled a long mountain run it went over 300 until I started down hill at 70-75 mph. It was an oven on wheels. The passenger side header melted the wheel well liner that was 6 inches away. The Jett Hott looked good bud did diddly squat for heat.

Bought new Thorley Headers, stripped the chrome plating and sent them to Swain for a coating that is true ceramic, much thicker (.002 to .015) than the Jett Hott and they did the inside as much as possible as well as the exterior. They looked not pretty. In fact they could be called plain ugly. But they worked a small miracle in that engine compartment. Temps fell to the high 150's and never got above 225 using in place sensors. I could pull a long mountain grade and the engine compartment remained below 200 even on the hottest days. I am convinced that the remaining heat is from the radiator and not the headers. You can put your hand to within 1/2 inch of the headers and not be afraid of singing your skin. All the heat was now going out the tail pipes. I actually saw about a 5% improvement in gas mileage after I did the coating.

Take a look and if you are more serious about reducing heat than having it look good go to Swain. There may be others that do it right, but they are the ones I know and trust. Straight shooters and no BS. They will tell you if you want pretty go somewhere else..

Swain Tech Coatings for engine piston coatings, race engine coatings, ceramic header coating, carbide metal coatings, thermal spray plasma coating, metalizing closures, spray welding

Not affiliated, and no financial interest in them, but they have been around a long time and have a superb record of being honest and real. My headers for the 3.0 or 24 valve are going there and all my engine parts are going to get their coatings.

Marcus McGee
 

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Discussion Starter #11
Can Swain coat used headers?
 

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Yes they can, but best to ask them. They need to be clean from rust and chrome qand need to be bare metal with no previous coating on them.

Marcus
 

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Discussion Starter #13
Marcus, thanks so much for bringing those folks to my attention. They are doing the real deal, where the others just fool around. I have often wondered why this technology not been given fuller expression: but it has at Swain! Now I am dreaming of giving my Ferrari engine the full treatment of internal coatings. (Ferrari headers are double wall, so no issues there.) But I have the same issue that you have - :D
 

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Well, just give me a ride in the Ferrari after they finish it. The only time I have ridden in one is at The Glen after I barrel rolled my B Sedan BMW 3 times and hit the 3 high Armco at 165. Got a ride to medical in one. But that is all I can tell you about it.

Marcus
 

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Is there a metallurgist in the house?

There's one question that has never been answered regarding the ceramic coating of cast iron exhaust manifolds.

The people at Zircotec in the UK are at the forefront of ceramic coatings over here. For many years they were part of the UK's Ministry of Defence and were involved in developing coatings for the aircraft industry etc. I went to their labs a couple of years ago and I swear I've never seen so many white-coated boffins in one place as there. I spoke to one of their experts about my manifolds, and the problem seems two-fold.

Firstly, their coating technique demands a scrupulously rust-free surface and they have never figured out how de-oxidise the internal bore of the manifolds, and then how to uniformly apply the coating. Secondly, and as a consequence of this first issue, they are only able to coat the outside of manifolds. According to their tests, this creates big problems for cast iron manifolds (leading to cracking), as too much heat is prevented from radiating from the surface. They did tests on internally coated manifolds but, owing to the cumulative effects of slight reversion and the limitations of their own application process, flakes of ceramic were coming away and damaging exhaust valve seats.

It follows that it seems, to my mind, that the best way of coating a cast iron manifold is internally, not externally. This means that the exhaust gases remain hot, promote scavenging, and do not seep into the iron manifold itself.

Plenty of people in here have now started to use ceramic-coated manifolds but there seems to be little real-world evidence to support the negative findings of the egg-heads at Zircotec. This leaves me in a quandary as to which advice to follow! Either the guys at e.g. Swain have cracked the problem of how to correctly coat the insides of manifolds and the guys at Zircotec haven't, or the latter are correct.

So how many people on this BB have had their manifolds coated, put some serious miles on the engine, and experienced problems, or none at all?

And as for my lay man's thinking, is there a metallurgist around here who could prove or disprove my thinking? :confused::confused:

Alex.
 

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The problem with cast iron manifolds my be true. But as to not being able to clean the inside of a manifold, that is rubbish. There are many ways to clean and even polish internal parts that are convoluted and hard to get at. You can use an immersion process to derust. and also a slurry that cleans and polishes as it is pumped through. It's been around for years and use all the time in industrial applications.

But, here I think we may be talking coating headers that are stainless or some form of tubular steel. They can be coated and it is done quite a bit.

Marcus
 

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Test results at Zircotec are the expected. Big differences in thermal expansion of both materials (ceramics and cast iron or steel) together with the thermal cycles to which exhaust manifolds are normally subjected (continuous expansion and contraction) lead to the separation of small ceramic “flakes”, which can damage the exhaust valves, catalyst…. this effect could be more severe if the base material is contaminated by oxide before the ceramic deposition.

As result of that, this isolation method is suitable only for applications where durability is not critical and where temperature differences during thermal cycles are not too big (motorsport applications, engines are always near full load)

A very common method used in sport engines is to use ceramic liners in the exhaust ducts of the cylinder head, these inserts are placed in position in the mould before the cylinder head foundry, and had an important thickness (3-4 mm). This technique is used to minimise the amount of heat transferred from the exhaust gasses to the coolant circuit.

In any case, external application of ceramic coatings in exhaust manifolds has no practical sense because the base material (cast iron or steel) will be subjected to excessive temperature (heat cannot be dissipated), leading to cracks apparition, premature corrosion, melted points… Same issues could be observed on wrapped manifolds

Best way is go for stainless steel, titanium or Inconel exhaust manifolds ($$$, but with lower thermal conductivity), and if more isolation is required, double wall with airgap technique could be used.

Paco.
 

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Paco, with all due respect to your engineering capabilities and the Zircotec people, you are talking apples and oranges. When I have the money to afford F1 type solutions I may take their advice. Till then the Swain and similar coatings work tremendously well in real world practical applications.


Maybe these coatings are not for daily drivers, and quite frankly are not needed for that application. If a backyard shade tree mechanic is building a pet project then they work quite well and have a proper place for that type of solution. From my practical and personal experience the Swain type of ceramic coating has worked well beyond what I expected and for over 35,000 miles in a motorhome that runs 455 cubic inches and with headers that used to glow red hot most of the time. Pushing 10,000 pounds of a barn door at 75-85 mph is hard hot work and the Swain coatings fixed my heat soak problems very well at a very affordable price.

If I need to replace the headers after 50,000 miles due to deterioration of the ceramic coating then I will be happy to do so. It is relatively cheap compared to your solutions.
Just because a solution is not perfect does not make it a poor choice when all parameters are accounted for.

Marcus
 

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I agree with Marcus. The aerospace industry deals with temperature levels and durations far above what most of us are working with. Same for the Formula 1, Indy, etc. crowd.

In the world of normal performance street-cars ceramic coating the manifolds inside and out has been proven to work well. There may be an issue with ceramic flaking off on the inside of the pipe at really high temps, and damaging the a turbocharger's turbine blades. I do notice most ceramic shops (including Swain) advise against coating the inside of a manifold upstream of a turbocharger. Other than that, I don't see a problem.

The GTV6 I sold had ceramic coating inside and out, and it passed Nevada smog for its new owner with flying colors, so I don't think the cat was damaged.

Greg,
hiperformancestore.com
 
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