Topic: Exhaust header and downpipe

[sharpxmen]

so last week i thought I broke another exhaust header bolt, not so, tightened all of them and still sounded like a tractor

so this weekend I took out the pacesetter header and downpipe

I found this




I had a Borla Stainless header i boght a while ago, it's not bad but not top notch either, it was for the TBI engine, it had the EGR and hot air thingy so i had to remove both. When i bought it i noticed the downpipe was 2'' diameter, stock is 2.25 - i figured it's time for an upgrade so i bought a J and a U Stainless 2.5'' mandel bent pipes. I also wanted to reroute the downpipe in front of the oil pan sump as i really didn't like the way it was between the sump and the transmission. I added the wideband and pyro bungs to the header as well.

This is the result of 2 days of work (i still need to wrap the downpipe, next weekend probably).





this picture is with the downpipe just hanging there but not tightened, it sits up higher




these are the way it sits, took the pics with the engine running - i was checking for leaks - I really like the Vibrant stainless clamps, they are rock solid but you need to be lined up dead on or will pull the pipes. I had everything tack welded together and they cut it in 2 places and put the clamps.

[Da_Skunk]

Nice work.

[grumpygy]

  That heat wrap may have caused the break in the old header.  Not sure why but it seems to make the metal brittle.  Had them wrapped on my old truck and had a good set of Hooker headers that were wrapped.  Dropped a wrench while working on the truck that broke the header open.

[FourbangerYJ]

Very nice!  I have heard that the wrap traps moisture. Can lead to the pipe rusting faster. Might not be a issue with stainless.

[neale_rs]

It looks great!

[sharpxmen]

thanks guys

there is rust on the outside surface no doubt, but still shouldn't have cracked like that. the grade of steel they're using is sub-par.

this time i got lava wrap, not sure why the hype about it but to me it feels like the fiberglass i used before was shielding better. The thing i like about it is that you don't need to wet it to get it to form around the bends and is not as bad on your hands (i didn't wear gloves and was ok).

I hope this header won't crack.
One thing I'm happy about is I can do an oil change without having it all over the exhaust

[jfrabat]

Nice work!  So....  When can we start placing orders?

[grumpygy]

Why Header Wraps Destroy Your Headers ... and
Why Thermal Ceramic Coatings are Recommended
 
Regularly we are asked about, or have commented on the use of header wraps (header tape, thermal tape, heat tape). This issue is a real pet peeve of mine. Good or bad about a product I will give my opinion based upon direct use and fact, and this stuff screams "Do Not Use on Exhaust Headers!"
 
THE FACTS:

    Header wraps are designed to keep the heat in the header to improve scavenging of the cylinders. Keeping the heat in the header allows the exhaust speed to remain high. (the right idea)
    Header wraps, by keeping the heat in the header, also reduces the radiant heat in the engine bay.
    There are no header manufacturers that I know of that will warranty their headers if any header wrap is installed on their products.
    In most cases the header wrap damages the headers beyond repair. (I will explain below)
    If you run a lean mixture, you "may" see a slim performance gain using header wraps. A rich mixture may show slim to absolutely NO gain in performance.
    If you do not mind replacing your headers and header gaskets regularly, and you like that ugly look of a wrapped header, go ahead and use the heat wrap.

BACKGROUND INFORMATION:
 
In the past, almost all NASCAR and other racing engine builders and crew chiefs used header wraps for the added power gains and thermal control benefits offered by their use. Problems occurred when these same teams had to replace the headers after each race (NASCAR) due to the wrap being about the only thing holding each header together. Most engine builders, crew chiefs, and definitely the header manufacturers themselves do not promote the practice of installing these wraps directly on the headers! They now utilize the thermal coatings that are chemically and electrically applied to the headers. Popular header coating services include Airborn, Jet Hot, HPC, and some header manufacturers now applying the thermal coatings in-house.
 
Imagine having to replace a $1500.00+ set of headers after each race weekend! Few but the most financially well-off race teams can afford to do this. Also, consider the downtime in remaking a custom set of headers. Most custom header makers do not have copies readily available.
 
I believe that the wraps are good to protect various underhood 'items' from heat, but not for the use of holding the heat in the header. For example: you can use the wrapping for the protection of fuel and oil lines, wiring, covering a starter motor, etc.
 
Cool air needs to be around the header, and insulating it with a wrap to hold exhaust heat in makes the header material surface temperatures reach near molten levels. When you wrap the header you trap the heat in the header, but also suffocate the material that needs to breathe to dissipate heat for it's own survival.
 
Please let people know our tech articles and links have updated
 
 
Engineers, Metallurgists, and other experts out there will state that there is no way that the material can fail because it was designed to withstand the internal temperatures of exhaust gases. This is very TRUE! But, when the header is not allowed to cool (or breathe) so as to dissipate those extreme temperatures that the wrap is controlling, you have now developed a heat absorption that compares to thermal friction. This causes temperatures to continue to rise beyond the normal exhaust gas temperatures (EGT's) the header material was designed to withstand. This holds true as with most any type insulation.
 
Try this experiment the next time you launder a load of bath towels and then dry them. Immediately pull them out of the dryer and just toss them in a snug pile on your bed. Now leave them there for a many hours, even a day, and then open them. You will find that there is still a considerable amount of heat left in the center towels. This heat, even though the outer towels and bed are normal room temperature have been able to contain their heat. This is a simple thermal insulation test, but compared to your headers you have an internal heat supply constantly coming from the engine when running. The heat on the outside portion of the header material is trapped between the wrap, and soon will begin to fatigue the header. This build-up of heat is amplified by the wrap. Your freshly dried bath towels do not need to breathe, your header material does.
 
The EGTs stay the same but the properties of the header material changes by amplifying the temperature due to the insulation. This action goes against normal laws of thermal dynamics, but this effect is fact, and you have to pull the ears off most engineers before they believe you. This is the trouble with plenty of education, but a lack of something that is often just as important, that of "common sense"! If you decide not to believe these statements that is your choice. Go ahead and install the header tape on your headers ... we'll be happy to sell you a new header set!

[sharpxmen]

Nice work!  So....  When can we start placing orders?

make an offer i can't refuse and you can have this one

[sharpxmen]

i got the downpipe wrapped and used some Thermo-tec mylar shields to protect the oil pan, will take some pics in the following days. I'm really liking the mylar shields, i can actually put my hand on it which is not the case with the wrap so hopefully will keep some of the heat away from the oil pan.

[dwtaylorpdx]

I'd add a cooler if oil temp is the concern..  I've always wondered how the tj style exhaust wraps so close ot the starter and does not cook it...

Dave

[sharpxmen]

i have an oil cooler.... just didn't hook it up yet (i have the adapter too but didn't get around to install it)

regardless of the routing either between the pan and transmission inspection cover or in front under the pan the exhaust radiates significant amounts of heat to the oil pan, the only better alternative would be under the transmission but then you heat up that one so really its no better not to mention the exhaust hanging another 2'' lower.

I still didn't get to take pics of the mylar shields, hopefully will do that today.

[sharpxmen]

here's the mylar, works pretty good - had it running today at idle for about 15 min and out of curiosity put my hand on the starter, it was cold to the touch.

[neale_rs]

Good stuff.  I need to get some for the passenger side floor where it gets really hot.

[sharpxmen]

Good stuff.  I need to get some for the passenger side floor where it gets really hot.

i have a second one that goes all the way to the muffler, however i would have preferred a wider one for on top of the cat as it's too small and sits flush on top of it - the idea is to have some space in between to isolate properly. it made a small difference though but still gets hot - i think there best would be to also have a screen like above the muffler with the mylar under it so it's screening but is away (without contact) from the cat and pipes.