To wrap or not to wrap. That is the question
- Thread starter cmaclean
- Start date
Andy Bettencourt
Super Moderator
Do it in two steps.
1. Heat sheild
2. Then as money frees up, coat it.
Header wrap is dangerous IMHO. When something goes wrong, it soaks up oil and catches fire.
1. Heat sheild
2. Then as money frees up, coat it.
Header wrap is dangerous IMHO. When something goes wrong, it soaks up oil and catches fire.
Ron Earp
Administrator
Did not. I never catch fire. 
In theory I think the wrap isn't such a bad idea. But, in practice, especially with a British engine that has the cylinder bore centerline laid over at 45 degrees, and hence the cam towers at same with header underneath, it is. Oil leaks are bound to happen as Andy points out and the wrap catches it. Have a rip or two around track at speed and guess what, you'll have yourself a toasty time!
R
In theory I think the wrap isn't such a bad idea. But, in practice, especially with a British engine that has the cylinder bore centerline laid over at 45 degrees, and hence the cam towers at same with header underneath, it is. Oil leaks are bound to happen as Andy points out and the wrap catches it. Have a rip or two around track at speed and guess what, you'll have yourself a toasty time!
R
Mike Mackaman
New member
Techline has a coating that can be sprayed on at home and cures by the exhaust heat. The coating that can be bought by a consumer is called Black Satin. I have it on my 260Z, notorious for heat issues with the carbs and it workes great. Not too expensive and easy to use, look good too. You do have to sandblast your header prior to coating, but if you ask around, someone has one they will let you use.
Mike
Mike
Definitely go w/the ceramic coating & heat shield. The header wrap was initially used on the Porsche turbo engines that utilize a stainless steel exhaust system. However, your basic over-the-counter header is not stainless, but merely steel tubing. And, in most instances, thin wall at that! The constant heat cycling & the trapping of moisture will eventually destroy a tubular header using header wrap. Never heard or saw header wrap catch fire, but, from what I have read here, it's easy to visualize. No longer involved w/in-line engines, but has anyone ever thought of using header wrap on the intake manifold (vs. the header) to prevent heat transfer?
Hotshoe
New member
Ron,
.... I guess you guys haven't tried all the products that are available. I use a "wrap" of sorts. And it does an excellent job. It is made by Thermo Tech and goes around the header and "clips" together at the seam.
.... I run a stainless steel header and attach a piece of expanded metal over the outside of the radius of the first bend after it leaves the engine. With exhaust temps @ 1700 plus the expanded metal holds the wrap off just enough to keep it from burning up.
.... I run it far enough down the pipes to clear the firewall and bends. This way it helps the velocity of the exhaust by keeping it hot until it gets to the less restrictive part of the system.
.... As far as longevity, I have been running the same header for eight years with only one header failure because of an accident. Thanks to JC Whitney they had the bend that I needed and I repaired it for only $20.00
.... Does it improve performance? Yes ..... How much? about 1 hp or almost 3 tenths in a mile and a half.
.... The wrap is made of fiberglass and a ceramic resin and it takes a "set" after its first heat cycle. And make sure that after you wrap it you start it up outside, it is really smelly and will make you eyes water .... been there done that ..lol
.... Rick Thompson
Jim Susko
New member
Header wrap and coatings
As usual, there is a lot of theorizing and speculating about this topic but little in the way of usable information. I have found that the only way to know the effects of something is track testing or dyno work.
Some years ago I tried header wrap on my IT Mazda and it killed the motor. I removed it in the next session and the motor came back.
Back then I wasn't dynoing the motor but when I finally got around to it I found I was running very lean. The header wrap might have made the motor run even leaner thus the drop in horspower. However, to know what was happening one would have to dyno the motor with and without coatings or wrap and optimize mixtures for each. Only then will you know for sure which is better. If you change the manifold, it is possible that the coating that helped before may now hurt performance.
This is because the optimum primary lengths and diameters may change with changes in exhaust temperature. Mass resonance and reflected wave tuning effects are sensitive to exhaust temperature which effects density and the speed of sound.
All this is theorizing, of course, and that is the point. The only valid way to know if it works is to test, test, test. So don't get caught up in the trap that everyone is doing it, or it worked for a particular motor or setup. Yours may be different.
One thing for sure is if you trap heat in the manifold with an external coating it will get hotter inside. If your mixtures are off a bit you can run 2,000 degrees exhaust temperatures in the rotary. The melting point of steel is about 2,500 degrees depending on the alloy. When it softens I don't know. But I do remember burning through a Racing Beat header--without a wrap or coating--when my mixtures were too lean.
As usual, there is a lot of theorizing and speculating about this topic but little in the way of usable information. I have found that the only way to know the effects of something is track testing or dyno work.
Some years ago I tried header wrap on my IT Mazda and it killed the motor. I removed it in the next session and the motor came back.
Back then I wasn't dynoing the motor but when I finally got around to it I found I was running very lean. The header wrap might have made the motor run even leaner thus the drop in horspower. However, to know what was happening one would have to dyno the motor with and without coatings or wrap and optimize mixtures for each. Only then will you know for sure which is better. If you change the manifold, it is possible that the coating that helped before may now hurt performance.
This is because the optimum primary lengths and diameters may change with changes in exhaust temperature. Mass resonance and reflected wave tuning effects are sensitive to exhaust temperature which effects density and the speed of sound.
All this is theorizing, of course, and that is the point. The only valid way to know if it works is to test, test, test. So don't get caught up in the trap that everyone is doing it, or it worked for a particular motor or setup. Yours may be different.
One thing for sure is if you trap heat in the manifold with an external coating it will get hotter inside. If your mixtures are off a bit you can run 2,000 degrees exhaust temperatures in the rotary. The melting point of steel is about 2,500 degrees depending on the alloy. When it softens I don't know. But I do remember burning through a Racing Beat header--without a wrap or coating--when my mixtures were too lean.
kophoenix32
New member
JetHot coating. We use on the Koni cup Subarus. Works great!
i had a motor fail (con-rod) and it holed the oil pan and the wrap caught the oil and then caught on fire.
jinx jordan on here does header coatings for a reasonable price. i gave him the header at the 2007 ARRC and then he shipped it to me when done. i at least saved on some shipping.
i won't use header wrap any more although i do have some wrap on the downstream piping to keep heat away from the cockpit.....
jinx jordan on here does header coatings for a reasonable price. i gave him the header at the 2007 ARRC and then he shipped it to me when done. i at least saved on some shipping.
i won't use header wrap any more although i do have some wrap on the downstream piping to keep heat away from the cockpit.....
It's my understanding that mild steel crystalizes and becomes brittle secondary to the heat from the wrap. Stainless gets stronger and doesn't crystalize. On the Opel we tried the wrap===PITA!! Then had a stainless header made and had Jet Hot coating applied---good deal!
On the Hondas, I'm wrapping the header but only where it's in close proximity to the left inner CV boot (have had that fail-due I think to the heat at that area when sitting still, ie grid, impound etc). Holed the block at NJMSP last fall and had an oil fire, but was not exacerbated by the wrap.
On the Hondas, I'm wrapping the header but only where it's in close proximity to the left inner CV boot (have had that fail-due I think to the heat at that area when sitting still, ie grid, impound etc). Holed the block at NJMSP last fall and had an oil fire, but was not exacerbated by the wrap.
I've read up on this, talked to some folks in the industry, and read stuff online (like Burns stainless site), and read some books on it... here's what they say:
> All metal gets weaker as you approach its melting point.
> Chrome plating causes hydrogen embrittlement of mild steel (google it). This is generally bad, and worse when you wrap it due to elevated temps.
> Header wrap can be a risk if you have a leaky engine or can't keep it clean. It will elevate temps in the tubes and steel will rot out quicker. Its not rusting due to water, but due to the elevated temps.
> Ceramic coatings seem to do the job well on mild steel, but several providers of the stuff told me its a bad idea to do on stainless.
> 321 Stainless is the best material (at semi-affordable cost) for headers, and not recommended to wrap it (not sure why)
> Don't wrap coated tubes, as you may just bake the coating off (not sure why else its bad).
So that's not science, but is the info I've collected over the years. I had a custom built header that was jet hot coated, and it broke a couple times. My current header is over 10yrs old, and holding up fine, and its chromed and wrapped. I like the wrapping just to keep the underhood temps down if nothing else. My next one will be custom built 321 stainless, with slip tubes and a burns 4-1 collector. Now I need somebody to make it for me
kophoenix32
New member
Way back when I had my ITB Volvo I had wraped the header,ran it for 5 years and never had a problem.
C
CDS
Guest
The header on my ITC CRX is wrapped where it is in close proximity to the radiator. No issues in 5+ years, but I only run a few weekends a year.
My engines didn't leak, and they didn't blow up, so never had any fire issues. Wrap is WAY better at keeping the heat in than any coatings. Although I did a ton of header testing we never did a wrap/no wrap back-to-back to see if keeping the heat in actually created better scavenging/velocity/hp, but I doubt it. Instead, the big payoff is underhood heat reduction which was always worth the pain in the butt to wrap the headers. To me.
We tried several coatings. Like wrap better. Learned to build our headers out of heavy gage tubing. Chrome NISMO headers held up really well under wrap. Our final custom stainless ones held up really well. The thick wall mild steel ones (.062 wall versus .040) held up until each successive evolution of our header design. Thin wall home made ones and the usual aftermarket suspects didn't last long under wrap, but had they been the answer horsepowerwise it still would have been worth a set of headers each season to reduce the underhood heat by as much as wrap does.
And you don't race Z's in the rain, so corrosion wasn't an issue either (on a quiet night you can hear the Z's rusting, so you don't exacerbate that by dragging them out in the rain). YMMV
We tried several coatings. Like wrap better. Learned to build our headers out of heavy gage tubing. Chrome NISMO headers held up really well under wrap. Our final custom stainless ones held up really well. The thick wall mild steel ones (.062 wall versus .040) held up until each successive evolution of our header design. Thin wall home made ones and the usual aftermarket suspects didn't last long under wrap, but had they been the answer horsepowerwise it still would have been worth a set of headers each season to reduce the underhood heat by as much as wrap does.
And you don't race Z's in the rain, so corrosion wasn't an issue either (on a quiet night you can hear the Z's rusting, so you don't exacerbate that by dragging them out in the rain). YMMV
vtluu
New member
Hmm. I'm about to attempt to wrap the Racing Beat stainless steel headers on my '99 Miata. The headers are below the intake tract and I really would like to keep the heat off the intake. The headers also run close to my side of the drivetrain tunnel and it'd be nice if they don't cook my leg.
My first thought was ceramic coating (the headers on my Evo 8 are coated) but the only shop around here (SF Bay area), as far as I know, that did ceramic coating moved to San Diego a year or two ago (Replika Maschinen).
My first thought was ceramic coating (the headers on my Evo 8 are coated) but the only shop around here (SF Bay area), as far as I know, that did ceramic coating moved to San Diego a year or two ago (Replika Maschinen).
Ron Earp
Administrator
My current 260Z header is wrapped and it seems just fine. The header is of beefy construction though but I've had no problem with the wrap and I think the underhood temps are definitely lower and more importantly the carbs/intake are cooler. Not seeing how a ceramic coating could achieve the same result with a 50 micron layer of coating on the header.
While I did have trouble with oil leaks on the old leaky Jensen motor that was more due to it's design than anything else.
Ron
While I did have trouble with oil leaks on the old leaky Jensen motor that was more due to it's design than anything else.
Ron