Alright, seriously, the guy who wrote this article has got to be kidding. I am a degreed practicing mechanical engineer and I almost fell over laughing when I read this part of the webpage:

"As you may or may not know from any education of standard thermal expansion physics, if you heat donut does it shrink or expand the hole? Of course since we live in a 3-dimensional world, it is a 3-dimensional reaction and it shrinks the hole! If any engineers want to argue this, start with your professors, not with me. I already know the facts and I have had engineering "students" argue this fact with me on numerous occasions."

He's about as wrong as it gets, but then I guess everyone is entitled to his or her opinion. (The hole does get larger, go look in any engineering text).

Then he writes:
"When the header is not allowed to cool so as to dissipate those extreme temperatures that the wrap is controlling, you have now developed a heat absorption that compares to thermal friction which will will continue to gain in temperature beyond the normal exhaust gas temperatures (EGT's)."

Hilarious, what the heck is he talking about? You can't get any appreciable raise in header temp above the EGT from "thermal friction".
If he's talking about Brownian motion, he's way out of his league (that's on the molecular level). If he's talking about friction caused by expansion of the headers and then rubbing on the heater wrap, it can't be much since the temperature gradients are not cyclical. You have to remember that you've got high flow exhaust actively convecting the heat away.

Here are real facts:
1. Header wrap will trap moisture and accelerate the rusting of your headers.
2. Header wrap is more effective than any coating available at a reasonable cost (Jet hot, etc.)
3. Header wrap will not cause the the headers to increase in temperature above EGTs.
4. The header tubes will see some applied external stress if the header wrap is tight enough to squeeze the headers when the expand from the heat. This will be minimal if the header wrap has any elasticity to it.

All that being said, I'll wrap my $200 set of Hedman Hedders and be happy to replace them every couple years if they rust out. It's worth the price of keeping the engine bay components from melting and the interior of the car cool.

 

Patience, I agree with you and so I will wrap my headers soon as it cools off enough to work on the car without passing out....

next summer I see the results....

GENE

 

Ya...but did you really think I meant wrap your side pipe headers so that the wrapping would stick out of the body lines?

Although, you would get better performance....

 

I know where you're coming form, but want to add, header wrap and thermal coatings do reduce underhood temps, but the extra few HP by keeping the heat in the pipe to aid in scavenging is the reason they began.

 

I thought Jet-hot coating reduced operating temps?

 

It may...never noticed it on my F-Body...i/e went from stock logs to SLP 1-3/4 JH'ed headers...buy gauge still acted the same.

Underhood temps decrease..as the temp is now exiting the pipes and not out the tubes into the engine bay/ect.

 

I wrapped my headers just at the sparkplug area to reduce the heat on the wires.

 

Ever thought about using Thermo-tec aluminized manifold blanket? Looks more water/oil resistant than cloth wrap.

 

Seems to me the jet-hot coated dynomax headers I have are cooler than the old stock manifolds and cooler than my unteated headers in my formula.