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pinoysurf
09-05-2004, 01:22 AM
Just wondering what the consesnsus was with heat wrapping headers. I've heard that it may cause thermal fatigue and ruin the steel wether it be stainless or mild steel. Just curious if the degradation is insignificant compared to the performance advantage of wrapping the header.

Nikeboy355
09-05-2004, 01:51 AM
what motor?... for NA applications I think it is fine but for turbo it might retain too much heat within the exhaust manifold and promote cracking sooner...

shane_B
09-05-2004, 08:39 PM
Is there any real truth to the above? I find it hard to beleive. If any manifold is insulated it will cut down on the amount of temp transients which is the real cause of fatigue.

allmotorKA
09-05-2004, 11:24 PM
I had header wrap on my old set of headers and after a few years some of the primaries were reduced to thin flakes of metal...I could crush areas of the header with my bare hands. The worst part is that since the header wrap covers the primaries, you don't see the slow erosion until its too late. This was on an NA motor. I will never use header wrap again.

JimStinksAtDorifto
09-06-2004, 01:56 AM
Header wrap only seems to be worth it on a cast header/manifold.

RDM_II
09-06-2004, 05:14 AM
Agreed. Iron doesn't seem to take too much of a beating, but the steel headers I've seen wrapped become brittle over time since the heat stays in longer, and it can also retain more moisture for a longer period of time. A local guy bought a used MSDS header that was already wrapped, we took it off a few months later and it literally fell apart coming off, there were a few places where the primaries had completely disentigrated.

OverZealousNoob
09-07-2004, 01:42 PM
I can't claim direct experience with this, so i'm just sharing info i came across.

this is taken from nissanperformancemag.com the "ask sarah" column. aug 2004

I have heard it said that in addition to decreasing the underhood temperature, header wrap also increases the flow rate of exhaust gases. If this is true, could you please describe the mechanism that accomplishes this?
Barron Keith
Golden, CO

The idea behind header wrap is the heat will stay in the header improving the scavenging effect of the cylinders. Hotter exhaust gases flow more easily. The problem is it works so well at trapping the heat in the header, it doesn't allow the heat to dissipate and temps will increase beyond the exhaust gas temperatures (EGT's) the engine normally sees. This heating and cooling causes the header to fatigue and will most likely end up damaged, increasing your chances of buying a new one! Nascar and other racing teams used to use heat wrap until they realized any extra performance they may have seen wasn't worth replacing the header after each race. Heat wrap is more meant to protect wiring, fuel and oil lines, fans, etc. from heat.

flip240
09-07-2004, 03:11 PM
^ Good post http://forums.freshalloy.com/images/graemlins/grin.gif

Dave562
09-07-2004, 03:42 PM
Header wrap should be considered a last resort solution. Every header that I've ever seen wrapped, eventually cracked and or flaked / shattered if you tried to take the wrap off. On my old L-series motor, I had to wrap the headers (and build a heat shield) because the carbs sit right above the headers. On hot days, the carbs would vapor lock. Wrapping the headers was the only way to get the temps down to the point where the carbs were happy.

Unless you have some sort of extreme situation like that, I'd stay away from header wrap.