Hey guys

I have a DC Ceramic header; and it gets really hot under the hood. I would like to wrap it with thermotec, but many say that it will crack the header within 6 months or so. IS this true? I just want to lower the temp.. Thanks

 

I heard it would, I'm gonna get some of the haetshield stuff, it's like a wrap around thing made out of heat resistant material. You can get it at summit for like $40 and you just wrap it around the header.

 

NO. I had this on different cars for years without any problems. Even crappy hedman headers dont crack after years of being wrapped. I think that cracking rumor only applies to turbo applications.

 

i too would like to get to the bottom of this...

 

cracking is usually caused by the header being wrapped too tight and with too many layers which does not allow your header to expand once it heats up.

 

Been hearing the cracked header story for awhile too. I wrapped a "massaged" EX exhaust manifold about 2 years ago, and it's still going strong. I know the stock stuff tends to be a lot tougher than most aftermarket products but after cleaning up the welds, they were significantly thinner. Still no trouble though. I've never seen a header cracked due to header wrap, and I don't know anyone that it's happened to either.

Under-hood temps went down 20 degrees! (set a remote thermometer sensor next to the intake and went for a drive) No heat shield or spray-on coating can come close to the insulative effect of header wrap. I can do a 2 hour drive, pop the hood with the engine still running, and stick my hand right down between the primaries. They give off about the same amount of heat as a radiator hose.

Supposedly, header tape helps with exhaust scavenging too. In fact, I think that was the original purpose of it...

 

I work with some people who were on the Nissan factory GTP race team, who said BAD things about the wrap. They showed me a stainless header which had been wrapped and it had these strange "stellagtites" growing out of the tubes, about 1/8" long.

I've talked to real (Indy) exhaust fabricators who also said wrapping is very bad. They said the reason they do get wrapped is to keep nearby composite bodywork from catching on fire, and also to keep the exhaust more efficient. They pointed out that the required life of a header on a *real* race car is measured in hours, so they get away with it.

I read an explanation of why 304 stainless headers sometimes crack. Around 1000-1400deg F, carbon is forced out of the metal, making it brittle - so it breaks. 321 stainless works better because while the carbon is forced out like 304, it happens at a higher temperature. So you might get away with 321 stainless, or inconel. Checkout http://www.burnsstainless.com. (it all costs a fortune, but that's what it takes.)

I'm certainly no expert on this, and I *really* would like to use the wrap myself. I just finished collecting all the tubing for my own 321 header. The flange was made on a waterjet (amazing machines.) I would NOT have wanted to make that stainless flange myself... The header is going into the car in my sig.

To quote Carrol Smith, "321 stainless is the ONLY material to make a header."

 

i have also heard from some people that it can keep your header from cracking. After you are done on the track, a usual header would lose it's heat, and maybe crack, but if you insulate it, the heat loss happens slower, so there's less of a chance. I'm not sure if this is true

 

Here is my experience with heat problems and cracking with steel and stainless steel. When a header is welded togeather many of the companies welding these headers togeather do not use enough filler rod on the welds, which is why you see a bit of a dip or low spot on the metal near the welds. When the header is heated up it expands and contracts during heating and cooling. When a header cools it all cools at pretty much the same rate all around and everything is fine. However when you add heatwrap to a header you are then changeing the rate that a header will cool and heat up, and in which areas it will do so at different rates. Which is bad as it will make the header expand and contract at different rates also. So let's say the areas that are cooling faster are pulling harder than the areas that are cooling slower which will casue the header to crack, and mostlikely it will crack at it's weakest points which is near the welds where the material is thin. Most of the cracked headers I have seen are cracked around the block flange or the pipe leading to the cat. This is because those two areas usually do not get wraped and cool the fastest after the engine is shut off. So in my opinion don't wrap a header unless you want trouble. The other option is a vented hood, but that can crack a header also. Let's say you drive the car and get the header nice and hot, then you wash the car or it rains and you get water on the nice hot header from the hood vent and it cools it down nice and fast causeing it to crack. I have had a few customers use that JET HOT coating on headers and havn't seen or heard any problems with that, I think the header is either dipped or sprayed with a heat resistant material. Also I have seen all types of cracked headers includeing stainless, steel, and cast iron. And those of you who think I'm just guessing or crazy I have worked at a metal fab and welding shop for 9 years and can't remember how many headers I have repaired... Hope this info helps.

 

>>work with some people who were on the Nissan factory GTP race team, who said BAD things about the wrap. They showed me a stainless header which had been wrapped and it had these strange "stellagtites" growing out of the tubes, about 1/8" long.<<

Aww c'mon. Will my daily driven "weekend racer" will ever see anything like the exhaust temps reached by a GTP car?

I'm also curious to know why the Indy guys think exhaust wrapping is bad. "Smokey" sure doesn't. And even though he comes from the low tech world of NAS(S)CAR, there is way to much $$$ at stake to take their methods lightly.

 

Never said you would, but like I did said, your 304 stainless or mild steet header will sit right in the temperature range where carbon will be drivin from the steel, making it brittle. You WILL be spending countless hours in that 1000-1400 deg F range, unlike a real race car who's header life is only a few hours, so they don't care.

The Indy header fabricator said the wrap is bad on a *street* car because it absolutely fries the metal. On their race cars they don't care because the needed header life is a few hours, not 100s or 1000s like a street car.

 

>>Never said you would, but like I did said, your 304 stainless or mild steet header will sit right in the temperature range where carbon will be drivin from the steel, making it brittle. You WILL be spending countless hours in that 1000-1400 deg F range, unlike a real race car who's header life is only a few hours, so they don't care.<<

I thought you were applying the 1000-1400 F range to the GTP car. Still sounds kinda high to me. I don't have anything to go on but fuzzy memory, but I thought exhaust gases (in a well tuned engine) were in the neighborhood of 800 F. Doesn't sound too much cooler, but a few degrees can make a big difference. I'm not debating the fact that the added heat from header tape can shorten a header's life span. But in my experience it's life can still be measured in years instead of hours. Maybe I've been lucky.

Awesome project BTW. I wish my wife were that understanding...

 

Just get a S.S. header coated.