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Technical exhaust wrap thread

Discussion in 'Traditional Hot Rods' started by nunattax, Jan 14, 2021.

  1. The wrap really does lower under hood temperatures, i don't believe some of the people replying here have every actually wrapped anything, you see it a lot on LSR cars because of the tight packaging and needing to keep heat out.
    With that being said, yes it does rust your pipes but sometimes you have to choose the lesser of two evils. I wrapped my fenderwell headers on the Henry J and after getting chastised here on the forum I removed it and immediately noticed a heat difference and I dropped a mile per hour at the track. When I redid my bike in 2014 I went back with the wrap and my pipes are still solid and not rotting off like was said it would do.
    I bought some used stainless fat fender headers last year, the craigslist photos showed nice shiny headers, when I got there they were wrapped, guy said he used them to break the motor in and a handful of start ups. I bought them and brought them home, I didn't care for his hose clamps holding the wrap on so I took it off, that shiny stainless was gone and a baked on rusty material pattern was left behind. I hit it with some 000 steel wool and a gray scotch brite pad and neither phased it, not sure the brand that he used or anything else like how cheap the stainless is but it definitely attacked the stainless.

    Screenshot_20210115-195539_eBay.jpg Screenshot_20201208-224413_Gallery.jpg

    The Henry J headers, like I said there was a noticeable difference in heat and heat soak with it on then with it off.

    blowby, warbird1, 31hotrodguy and 2 others like this.
  2. I don't think that the pipes are rusting because the wrap holds water. IMHO what is happening is the metal is getting hot enough that it oxidizes without water. That temp changes depending on what type of metal it is.

    The only pipes I have ever wrapped were titanium, on an off topic bike. The pipes ran right next to a fiberglass fairing. I coul dnever get over the thought I was likely killing a $1000 pipe to save a $150 belly pan, so the next winter I cut the fairing down to clear the pipes and took off the wrap. Much more better.
    Last edited: Jan 15, 2021
    5window, 61SuperMonza and Stogy like this.
  3. Stogy
    Joined: Feb 10, 2007
    Posts: 21,742


    There's lots of options here and so many things factor into how something is going to deteriorate...but failed anything will require possible re & re and will have factors leading to failure...

    I'd think the outside use is more modern inspiration but use of similar insulation may have been used by big auto, race...and possibly some street...

    I look at a lot of vintage Hotrods and the use of this wrap is something I haven't seen much of...The flexible ribbed tube was sure around...

    Black Cloth tape around springs as well...

    I'll all for using modern as opposed to old school asbestos sheet to achieve a temperature insulator...I certainly think it could reduce burns but I've only touched the uncovered pipe and you don't forget that...:eek:
    Last edited: Jan 15, 2021
    loudbang and Lil32 like this.
  4. I wrapped the head pipes on my 39 sedan because of the routing around the steering box and then down thru the cross member and next to the master cylinder. I didnt want to but it does make a big difference in the heat to close components. has worked fine for over a year, id rather lose an exhaust pipe than cook a master cylinder or steering box.
    20190907_235936.jpg 20190907_235914.jpg 20190907_212838.jpg
  5. flat-ed
    Joined: Oct 19, 2020
    Posts: 13


    Most header builders void warranty if wrapped...something to think about.
    Lil32 and Stogy like this.
  6. Stogy
    Joined: Feb 10, 2007
    Posts: 21,742


    ...this icon might have its gases exiting warmer...
    I like the Stripers humor with the T Coupe..aka windows...:D


    Credit to Photographer, Owner
    loudbang and Lil32 like this.
  7. Most headers if you wrap them it will void the warranty unless they are ceramic coated.

    I like the look but it seems like header wrap was not even a thing until the '80s or '90s. ;)
    dana barlow likes this.
  8. nunattax
    Joined: Jan 10, 2011
    Posts: 2,769

    from IRELAND

    Stogy likes this.
  9. Wrapping the headers is not to keep heat out.

    The theory is to keep the heat in the headers to help with scavenging. There are those who buy into that theory and those who have conflicting data that disproves the theory.
    Stogy likes this.
  10. 61SuperMonza
    Joined: Nov 16, 2020
    Posts: 489


    As we all know, there will always be a trade off. Any mod will always have a "joker".
    It's a matter of balancing the performance with reliability and there are many factors that will determine what those mods are for each individual build.
    I always ask for opinions, but I do my research as well.
    In my case wrapping the exhaust was well worth it. The HP increase as well as reducing operating temps outweigh the issue of rusting pipes.
    03GMCSonoma, nunattax and Stogy like this.
  11. typo41
    Joined: Jul 8, 2011
    Posts: 2,572

    Member Emeritus

    We wrapped in the Circus because you sit right above the exhaust and you get a hot butt making a run,, hot enough to feel through the fire suit,, also the exhaust melted our belts that were above the floor boards(before wrap) , that was expensive
  12. 57JoeFoMoPar
    Joined: Sep 14, 2004
    Posts: 5,137


    I have certainly heard of the positive effects of keeping the heat within the exhaust, but if that were the main goal, it would seem a ceramic coating might be a preferable method. I can say from experience that we wrapped the headers on an O/T SBF powered race truck my FIL put together, and they got oil soaked from a prior leak and caught fire.

    I used some header wrap not necessarily in my headers, but on my exhaust pipe where my speedometer cable was close to it. I just attached it with regular old safety wire.
    Stogy and Budget36 like this.
  13. Harv
    Joined: Jan 16, 2008
    Posts: 285

    from Sydney

    I wrapped the fenderwell headers for the 327 Chev in the Holden wagon in my avatar. I used the DEI wrap, and their stainless zip ties. The Holden wagons are about a 3/4 scale '57 Chev.... there is room in the Chev engine bay for a small block, but the Holden engine bay is narrower. The exhaust ends up close to everything, no matter how hard you try... brake hoses, fuel tank, master cylinder, steering rag joint. All stuff that I don't want getting hot. Using the modern aluminium laminate shields would be difficult, and look worse than the wrap IMHO. I've oil soaked mine (blew the dipstick out... or perhaps left it loose :oops:) and it did smoulder but soon cooked out - perhaps I was lucky, though the oil volume is pretty small.

    5window and Stogy like this.
  14. Budget36
    Joined: Nov 29, 2014
    Posts: 7,536


    Wrap does look cool, but ceramic coating inside and out like JetHot does, can make a plain steel, non chromed header shine with minimal upkeep.
    5window likes this.
  15. Mike Colemire
    Joined: May 18, 2013
    Posts: 1,394

    Mike Colemire

    I've used it on starters the were close to the headers. I think it has it's benefits, like on my side pipes but as far as looks I hate it. My exhaust will be under the car as soon as I can do it. I built a blown small block and put in a corvette that the guy insisted on these big chrome side pipes he had bought. I burnt my leg on the damn things several times.
    Stogy likes this.
  16. Wrapping the header/changing the temp is similar to changing the tube lengths. The pressure pulses (which are not the same as the exhaust flow) travel faster in hotter temps so the pipes are effectively shorter. If that's benefical to your system then wrapping will help. If not, it won't.

    Fun fact - exhaust gasses get more viscous as temp rises so the hotter the flow the more restrictive it is, opposite of what most people assume. The good news is, restriction in the exhaust isn't as critical as some would like to believe.
    Stogy likes this.
  17. Gearhead Graphics
    Joined: Oct 4, 2008
    Posts: 3,852

    Gearhead Graphics
    from Denver Co

    Did it on an off topic motorcycle with stainless header. It did cut the heat on the seat A LOT, which was good. The exhaust had a neat deeper tone to it after the wrap as well.
    The bad, it caught moisture all the time and would steam forever, smelled funny when it was hot. And it made the stainless oxidize/stain quite bad. I ran it for a couple years. once it started to unravel i pulled it off and when i saw the damage done I didn't replace it.

    It has a use. Just wouldn't put it on everything
    5window likes this.
  18. grdra1
    Joined: May 20, 2013
    Posts: 390


    Wrapped my headers today, Used stainless filler wire and T clamps to hold in place, happy with result. Glen 297.JPG 303.JPG 306.JPG 308.JPG 310.JPG
    Stogy, Maicobreako, nunattax and 2 others like this.
  19. loudbang
    Joined: Jul 23, 2013
    Posts: 39,685


    16 years same stuff and still going strong on OT cars header with SS exhaust no leaks rust or errors. :)
    Stogy likes this.
  20. To slow down fraying, start t the back and work toward the front.
    Stogy and loudbang like this.
  21. lancew1959
    Joined: Sep 9, 2006
    Posts: 33


    IMG_0331.JPG I wrapped mine because my 4 year old son was watching me sync the carbs and burnt his hands pretty bad on the headers plus it helps keep the heat down when I’m standing over the engine trying to sync the carbs. It’s probably not as cool looking but I feel a little better having my son around it.

    Sent from my iPhone using The H.A.M.B. mobile app
  22. gif
    Joined: Nov 9, 2016
    Posts: 1


    I custom built these with baffles and spiral mufflers 5-6 years ago. I thought I heard an exhaust leak and when I cut away the wrap this is what I found. I think failure was caused by the combination of high heat and back pressure. When I build the replacement set I will NOT wrap them.
    Last edited: Sep 28, 2021
  23. loudbang
    Joined: Jul 23, 2013
    Posts: 39,685


    Too many layers in the same spot causes that.
    egads likes this.
  24. MAD MIKE
    Joined: Aug 1, 2009
    Posts: 690

    from 94577

    If your exhaust was making that much back pressure, you would have other problems.

    Unequal length primary tubes welded together will stress each other from different rates of expansion/contraction due to the different lengths and heat concentration. Eventually headers, that merge into a collector, will crack. Don't try to fix the crack by reinforcing the weak point, it will just shift the stess/weak point to a different spot and you will be chasing the crack problem.
    Yup, it will eventually crack. The more the car is driven the more likely it will crack sooner.
    The more stresses the header will experience the quicker it will crack. Headers should not support the exhaust, yet the exhaust needs to be supported in a way that it is allowed to move freely during expansion. Constraining the exhaust will cause cracking and transmit excessive noise into the chassis.
    Stogy and DesmoDog like this.
  25. Yeah, what he^ said. The crack is likely from thermal stress, the more heat cycles it sees the sooner the cracks happen. Wrapping the pipes raises the temperature of the tubing and the metal has a limit as to what temps it can handle before it starts oxidizing. Those pipes are oxidized and it's not from rusting. Some people think the wrap absorbs water and promotes rust, but at high temps it'll happen without water.

    I'd also agree backpressure had nothing to do with it. For what it's worth I developed OEM exhaust systems for about 30 years (retired now) including about five years of durability testing. Backpressure isn't nearly as much of an issue as people think it is.
    MAD MIKE, loudbang and Stogy like this.
  26. Stogy
    Joined: Feb 10, 2007
    Posts: 21,742


    I wouldn't doubt the pipes get to the point of a low glow many times unnoticed and combined with the constant pounding of our very smooth roadways add stresses that further exacerbate the other issues...
  27. Flat Roy
    Joined: Nov 23, 2007
    Posts: 491

    Flat Roy

    The way to avoid the problems of wrap is to build your headers out of Stainless Steel. No rust and will retain heat for good exhaust flow.:rolleyes:
    loudbang likes this.
  28. MAD MIKE
    Joined: Aug 1, 2009
    Posts: 690

    from 94577

    I'm geeking out a bit. Love hearing about OEM development.
    Stogy likes this.
  29. SS327
    Joined: Sep 11, 2017
    Posts: 446


    We wrapped the headers on my buddy’s 69 superbee 440. Worked great all summer. In the winter from heating and cooling back off while working on the car. Moisture built up in the wrap and turned the Hooker Super Comps into dust on the first start. It was kind of funny but sad. The next set were jet hot coated and we never looked back and never had another problem with heat and rust.

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