At Thorley ceramic headers only cost $150 more and I understand they really cut down the heat.. comments??

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Wow! For $150, I think I'll keep the header wrap on mine, let them rust out, and then get the real deal. After all, I'm spending my kid's inheritance. The Thorley people also advised to dip their headers in something called jet hot. They said it cut the heat down but I don't recall what they said about the degree decrease

Jet Hot is good, but way overpriced. There is a ceramic powder coating you can do yourself if you can bake the headers.

I talked with Jet Hot, they sell Hedman Headers. The ones to fit a 1985 454 Class A motorhome are $399.00 coated. Thorleys with their ceramic coating is in the high $500's. Of course Jet Hot says their coating is better and they charge $279.00 to coat someone elses headers.

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I bought the Hedman Headers and their coating is not as good (thick) as the Jet Hot Coating. The ideal would be to have stainless steel headers with Jet Hot.

The Hedman headers referenced above for $399 are coated with Jet Hot.

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I just bought a set of headers from an outfit close to Seattle. It is called Stan's Headers. I had them coated with a ceramic coating that cost me $279.00. It is black in color and the outside and inside is coated. They told bme that the engine will cool better and there will be less heat in the engine compartment. The total bill was over $600.00. That included the bolts, gaskets and the adaptors to hook up to your tail pipes. They are the tri-Y design. They seem to be quality product.

My (unsolicited) opinion: The idea of headers (and Doug Thorley is the King) is to be paired with a free-flowing exhaust to quickly clear the system while "sucking" the exhaust from the cylinders, avoiding heat build-up in the block, head, and manifold. If the headers/exhaust system is working properly, ceramic coating and such are a waste of money. If the coating is to contain the heat inside the header pipe, it voids the intent; if it is to absorb the heat and radiate it off the pipe, it is adding to the engine compartment heat which, again, is a bad idea. Get a good set of Thorleys, paired with a free-flow exhaust, and relax.

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"You are what you drive" - Clint Eastwood

I have put Thorleys on two RVs and noticed lower doghouse heat on both. They come nickle plated.

Hi Gunner,

I asked that exact question of the Jet Hot guy. It reminded me of a movie where a guy invented a spray which made dog poop disappear. After awhile people started asking where the poop went.

So I ask, where does the heat go? He told me that it is sinked to the cooler exhaust pipes and outside atmosphere thereby creating a vacuum and evacuating even more heat and exhaust from the engine, increasing horse power as a result. Bill is this the air sucker theory??

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Well, I'm not sure I would call it "Air Sucker" theory, but it is often called scavenging.

A 1 to 5% power gain is claimed by the more honest coaters. Header wrap increases power more on lean engines than on rich ones. Sometimes no power increase on rich running engines.

It doesn't take much of a stretch to call headers "air suckers." Scavenging occurs because the inertia of the moving exhaust gas column creates a pressure drop that pulls (sucks) more exhaust (hot air) out of the combustion chamber before the exhaust valve closes. Headers work (if the rest of the exhaust system flows freely) because the sweeping curves in the header tubes allow the hot gasses to exit smoothly instead of with turbulence, as in a typical cast iron manifold.

Reducing back pressure, reduces the length of time the hot exhaust gas has to transfer heat into surrounding materials, so headers run cooler when the vehicle is underway. The thin steel of headers radiates heat more quickly than cast iron, so headers cool faster after shutdown. This reduces the amount of cooking that takes place in the engine compartment in the absence of air flow.

Combine these factors, and you have the reason for Bill H's experience with cooler engine covers when headers are installed.

I don't know why coatings or header wrap would increase power output, unless retaining the heat a little longer adds velocity to the departing gas, thus increasing the scavenging effect.



[This message has been edited by olroy (edited May 24, 2005).]