I just went to a local ceramic coating shop to drop off my Hooker LTs. The owner gave me the full tour, and showed me their product. This stuff is amazing. Not the cheap stuff most use, that only lasts a year (not to name names). This stuff is stable to 1800 degrees, as he demonstrated with a torch. He got a piece of metal glowing red! Let it cool, and with a little polishing compound, and some steel wool, it shined like before in seconds We then bent the metal back and forth, abused it. Then looked at it under a microscope. It didnt crack, or hurt it at all!

Anyway, the most impressive thing I saw was their proof coating the inside of headers hurts power badly. They have an engien dyno. With a small block chevy with 450HP with his coated headers, there was a 12% loss in power with the same headers, coated on the inside Thats a 54HP loss from nothing more than coating inside the header! He said it makes the header too resistant to heat, and keeps that heat in the engine. That is crazy.

Anyway, they are coating my headers, and now Im taking them my intake, valve covers, possibly my oil pan, and whatever else I can think of. If I had the time, Id have them coat my combustion chambers, pistons, rods, crank, and bearings too. This is very impressive stuff.

Website: www.cradin.com

Check out the racing pics. The coated rod bearings still look great! Those main bearings were out of the same engine, and werent coated. Huge difference.

 

Hmm...interesting.

 

I guess the tech gurus like Ray Bohacz, David Vizzard, the people at Swain Technology, Jet Hot, etc. are just fooling us with their unreasonable claim that keeping the heat in the primary tube increases power by increasing primary velocity to increase scavenging. You just can't trust anyone any more.

 

How does the coating on the inside of the primary keep the heat in the primary? If the coating does its job, it wont hold heat. This guy says an uncoated and hotter inside primary helps scavenging more. As I said, he did back to back dyno runs, and got a 12% power loss with the primary's coated inside

 

If the exhaust gases are hot, the only way for them to cool down would be to transfer their heat to the primary, and then out into the atmosphere. By insulating the tubing with ceramic coating, youre lowering the heat transfer coefficient between the inner primary tubes and the atmosphere.

 

It's my understanding that the primary mode of heat rejection from coatings is by reducing heat transfer through radiation, maybe some through conduction but the coatings are thin anyway so I'm not sure how effective that would be. Without a coating the hot exhaust gasses allow heat transfer into the steel pipe, lowering temperature of the gas, and reducing velocity.

How would a coating keep "too much heat in the engine"? The exhaust gasses are already evacuated from the cylinder, the heat either goes out the tailpipe or is transferred to the pipes and radiated/convected off of them.

Why do successful engine builders use coatings? I'm assuming coatings are allowed in many classes of racing and wouldn't be surprised to see them used there as well but I can't say for sure... anyone? Bueller?

Furthermore, if anybody actually believes that a coating could result in a 12% gain or loss of power, I've got some other things to sell you. This guy sounds like quite the salesman to me

I'm not an expert but logically it doesn't make sense. Also, the real experts also disagree. The only reasons not to use an internal coating is money (this might be part of his reasoning) and possible damage to a turbine, IMO.

 

Could it be though that a coated primary interior makes the steel cooler and slows velocity? And after the non coated primary warms, it helps velocity.

All I know is that all the local racers work with this guy. He has years of dyno R&D, and the dyno dont lie.

 

Even if it does or doesnt transfer heat, 12% is still bull ****. Are you sure they were the same type of header?

I think this guy plays with imself a bit on the 12% ****, but they do sound like quality coating if it withstood being red hot and bent ...

 

Heat leaves the exhaust by flowing through the metal of the primary tube. The interior coating "reflects" the heat and stops it from entering the metal of the header tube. With the heat held in the exhaust gas, the density of the gas is lower (perfect gas law - density is proportional to absolute pressure and inversely proportional to absolute temperature). Since the density of the gas is lower, it has more volume per unit of mass. The only way it can flow the same mass through the primary is to flow at a higher velocity. That increased velocity increases the momentum of the gas and strengthens the scavenging pulses. These coating were developed to help reduce heat transfer to the blades in gas turbine engines.

I'd really like what you said to be true.... by scraping the interior coating off my AS&M headers, I could pick up..... let's see.....

800 / 0.88 = 909

Hmmmmm.... 109HP increase, simply from scraping the coating off. See how silly it sounds.

 

My biggest concern is that though he may well in fact have years of dyno time he is also selling something. You can make a dyno say all kinds of things. It's not lying but that doesn't mean the experiment has been run scientifically. Same headers with nothing different but the coating? Engine tuned for maximum power for each scenario? Conditions and correction factors used? No matter what, 12% is flat out ludicrous. That tipped me off right away that he's either full of crap or has made some big mistakes in running this experiment.

As stated before, there are plenty of guys that disagree. These guys have made winning cars and have written books on the subject. It's very hard to argue against those credentials, very hard.

As for the mode of heat transfer, again I'm not all that well versed on coatings. You have to keep in mind that you only have so much thermal energy in this system. Generally speaking if the pipes are hotter, the gasses must be cooler. It's simply a balance. It's a bit more complicated than that because you must look at heat transfer from exhaust gasses to pipe and from pipe to ambient air. You must also consider the different modes of transfer between convection and radiation. Similar coatings are also used on pistons to keep pistons cooler and retain more thermal energy in the combustion gasses... what's he say about this?

 

He uses the same coatings on pistons. He coats everything. I agree the 12% thing has got to be a sales pitch. Something isnt right there. I just thought this was interesting.

Either way Ive got a coating that will last a very very long time

 

Yeah Jethot coating is supposed to last forever as well... which it would if the set of headers coated were boxed up for eternity but in the real world scenerio it really only lasts 1-2 years.

 

Well, isn't his ideas about interior header coatings in contradiction with piston coatings?

That's the important thing

 

well said, the coating on the headers toward the underbody of my car is shot to ****.

 

I don't believe for a second that coating -or not coating- a set of headers is worth 54hp. I also don't believe that your engine gives a rat's *** whether the coating is on the inside or the outside of the header. That claim ranks as one of the more asinine things I've heard from an industry full of asinine claims.

Think about this: when a header is designed, I assume the engineer is trying to make a certain velocity in the primaries for a certain application (actually I assume they are not engineered at all). If you increase the primary diameter from optimal, you drop the velocity below the optimal level and you expect that power will suffer, right? Now, if we reduce the header diameter from optimal we would speed velocity and again we expect power to suffer, right?

So how is it that somebody can claim that adding a heat barrier on a header always increases power? Logically that can't be true.

If a header is correctly designed, the primary size lends itself to the optimal velocity for that engine. If you add a head barrier you speed the exhaust gas and now the primary cannot be the right size. It must be impossible that it can work in our favor in all circumstances.

In the case of stock 275hp LT1s I could believe that thermal barrier coatings would help. That engine needs a smaller primary so speeding the exhaust with the coatings might very well be a benefit.

Ever notice that Cup teams do not use heat barriers on their headers? There must be some reason.