Powder Coat for cast iron exhaust manifold...

[Insoc]

Hello all!

Yesterday I installed freshly high temperature powder coated exhaust manifolds... I am including pics, but I have a question...

The place gave me a lifetime warrenty, but already the coating has cracked on manifold 2&3... Am I wasting my time, or is there a chance that one was not prepared properly? They said it was good for 500 degrees, and they had other people's exhaust manifolds that had been done, so it is nothing new to them. I just wonder why mine cracked already...

Thanks!

[Alleggerita]

Personally, I am not enamoured by powder coating much. Whenever I have used powder coating in adverse environments it hasn't worked for me and I actually prefer regular piant coatings that can be much more easily repaired.

For exhaust manifolds I would recommend either ceramic coatings - their usual temperature range is somewhwere from 1200-2000 degrees F. Alternatively, the exhaust manifold from Eastwood comapny does a great job for a lot less money if temperature management is not crucial.

[Insoc]

It was convienent. I took them in to get blasted so I could paint them, and they said they could high temp powder coat them. I thought, what the heck! Now I need to know if I am wasting my time with getting it fixed...

[Gordon Raymond]

I too have not had much luck with high temp. powder coatings. This technique works quite well for most engine components, but for manifolds I use VHT paint and repeat as necessary(race stuff that's rebuilt regularly) or Jet Hot for things that will stay together. I have had no Jet Hot failures, even with pitted tubular & cast iron headers.

I believe your problem may come from a "heat soak" situation, where the headers get hotter than 500 deg. after the engine is shut down. This is not unusual with cars using catalitic converters. If you spend the time and effort to fix it, send them off to Jet Hot. Just my opinion.
Best, Gordon Raymond

[Geezer]

Jet Hot gets my vote.

[AndrewO]

Hi Insoc,

If they gave you a lifetime warranty you have nothing to lose by going for a drive over there and showing them what happened. There might be better coatings but why bother if you can get yours fixed for free.

Let them have a look and then arrange for the repairs when it is convenient for you. At least you'll be booked in and they know it was an early fault when you come back in 6 months to have it fixed.

Good luck

[Insoc]

I have a spare header they can prep and coat while I use the car...

And for the record, cast iron headers do not need jet coat, nor do I want to ceramic heat retention coat them, I simply wished to prevent some rust by having them painted/coated. Cast Iron retains heat very well, and all jet coat would do for me is make them very expensive...

Thanks for the replies so far, and I hope to learn more from this!

[Damo105]

Someone correct me if I'm wrong, but I thought the purpose of having headers ceramic coated is not for heat retention, but for heat dissipation.

My understanding is the ceramic coating deflects a lot of heat out the back of the exhaust, thereby lowering the engine bay temperature.

[velocedoc]

If the headers are properly prepared, the Eastwood paint is perfect for the headers. I have had excellent results, and it doesn't burn off.

[Curtis]

I love powder coat, but that is just to hot a spot for regular old
powder coatings. The exhaust gas traveling through the header
very close to the port consistently exceeds 1200 degrees when
the engine is under load.

[Insoc]

Thank you all for your responses...

Velocedoc, my previous headers were painted with Eastwood high temp cast iron paint, and I was very happy with the results. However one was cracked so I had to replace it. This new coating was a act of convience for me, my plan was to paint it with my eastwood paint, but the high temp coating sounded like an easy way out for me, and now I wonder if it will work or not.

Curtis, it is not regular old powder coating... I don't know what it is, but it is high temp powder coating. The place charged more for it then regular PC. They charge $10 a pound for normal powder coat... This cost me $125 for the two manifolds. They have been in business for 18 years, and they had other customer's headers/manifolds coated with this stuff waiting for pick up, so this is something used in this manner. I just wonder if an Alfa is different then your standard V8 log manifold, that is cast iron, and I assume generates the same heat... Which leads me to believe there is simply a problem with the one manifold's coating, or one of you can tell me what I am missing!

Damo105, my understanding of Jet hot is as you described it, we are suffering from semantics... When I say retention, I mean less reflected/radiated heat to the engine bay... Cast Iron is already very good at heat retention therefore Jet Hotting/Ceramic coating cast iron is not neccessary. However steel headers radiate heat like mad, hence the exsistence of Jet Hot, to replicate what cast iron already does so well...

[velocedoc]

The JetHot coating is coated inside and out. This coating makes the heat travel down and out rather than be retained by the metal. This process is an excellent way to have 750-101 headers treated as it will make them last virtually forever. I have yet to hear of a dissatisfied customer.
Thank you for your explanations, be sure you get back to us on how all of this is resolved. Pictures would be nice

[Insoc]

Cast Iron hardly radiates any heat, almost all the heat is retained in the Iron and is passed to the exhaust so I believe ceramic coating to be unecessary.

However I do believe that all Jet Hot customers are satisfied with their work and ceramics performance.

[Gordon Raymond]

Ok, lets talk about headers, both cast iron and tubular. I have used infared temperature sensors with many engines on dyno's in the last 40 or so years. Cast iron: Retains heat, but as the engine is running directs the majority of the heat away, thus use with cat's. External coatings do little to change external temperatures WHEN THE ENGINE IS RUNNING. Colors do make a slight difference, darker colors radiating heat more than light colors. Matt finishes, radiate slightly more heat than glossy. WHEN THE ENGINE STOPS RUNNING, cast iron "heat soaks" and becomes slightly hotter. Some of this may be due to catalitic shut down. Ceramic internal coatings on cast iron lower exterenal temp's. when running. At shut down, the headers still "heat soak".
Tubular headers: When running, considerably higher external temperatures with either type coating, same color and surface texture temperature changes as iron. On shut down, very brief temperature rise, less than iron. Overall with tubular, higher under hood temperatures. Internal ceramic coatings reduce temperatures just slightly, not as much as with cast iron.
Usually, cast iron is used with cat's, as more heat is passed to the converter WHEN RUNNING. Tubular, though used with converters, also "light up" the converter, but not as quickly.
Of the various treatments available, a glossy Jet-Hot coating, internal and external, will reduce RUNNING under hood temperatures with either cast iron, or tubular, more than Eastwoods, or Powder Coat.
Eastwoods is much like VHT, but lasts longer and is external only. Powder coatings heat curing properties MAY not match up with header running or shut down temperatures. NEW IRON HEADERS, not coated with carbon internally, heat MORE running and "heat soak" more on shut down. Powder coat on NEW iron is more likely to fail than on used iron.
I have never used Powder Coated tubular headers, so cannot comment.
This is all MY observations, and opinions. An engineer can probably tell us WHY all these things happen with Iron and Tubular headers, with the various coating systems available. For street applications, all options can be used, with differing results noted. For race applications, under hood temperatures can be critical, and options are more limited. I hope my observations have helped. I have not given any temperature NUMBERS as they vary with engine, engine tune, and the measuring tool, as well as how the tool is used. Gordon Raymond

[39cub]

Hi, Guys,

I've had Jet Hot do some headers and exhaust components and I'd recommend their service. They have several colors including 2 grays that look like freshly sandblasted cast iron. Prices are reasonable and, if you let them coat the insides also, they cover the application for life. Check them out at http://www.jet-hot.com. Ive also had good, but not perfect, results with the Eastwood (others have it, too) Stainless Steel exhaust paint applied to thoroughly degreased and sandblasted cast iron headers. Downside is that the paint must be applied thick and it always looks like paint, whereas the Jet Hot coatings don't.

Chuck