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I wouldn't, it's made out high quality stainless steel that is made to handle the stresses of repeated high heat applications.

Besides I'm sure HPC would want you to coat everything if it was up to them;)

IMO listen to Greddy on that one.
SH
T78
 

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Discussion Starter #3
I'm glad to have heard your opinion on this. I had more-or-less already decided not to coat, but you've help confirmed it, for both of the reasons you cited.

Thanks!

John
 

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Hence the benefit of tapping into the collective knowledge of the Forum ;) . I love this place !

I also emailed Derek Wang of T04r.com about this. I doubt he'd mind if I shared his feedback on the issue. He said there has been some flaking on the outside of his manifold - even with a 1600 degree coating - and that it could be happening on the inside too though he hasn't looked.

I guess it's a trade-off either way. The manifold will last longer uncoated but heat build-up is a problem. I'll keep the $200 and deal with the heat instead.

Maao said:
Ah crap. I wish I knew this before I had them JetHot coated. :mad:
 

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Anything you can do to retain heat and keep underhood temps down is a good thing. I would DEFINATELY coat the header. Use Jet Hot 2000, that shit will never come off....
Peter
p.s. expanding of a stainless steal .25 inch thick header? No chance guys, 1600 F is not enough make it expand in such a way that it will crack the coating. The 1600 is cracking b/c it can only withstand around 1600 F and he has hit more than that...
 

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I'm qualified to answer this!

Here's the deal:

Whatever you do, DO NOT use header crap...er...wrap on your manifolds or downpipes!! Regardless if it is stainless or not, the life of the object wrapped will go WAY down. I used to work for a well-known manufacturer of automobile and motorcycle turbosystems. All we ever fabricated was made out of 304 or 321 stainless, or SCH40 pipe. We have used EVERY product available. The wrap merely traps moisture during cool-down...

As far as ceramic-coating goes, we used it frequently on turbine housings, headers and downpipes. Outside coverage IS recommended, but do NOT coat the inside of the pipes! The material INSIDE is what melts/cracks and ends up inside your turbo! OUTSIDE good, INSIDE bad.:nono:

Cheap plug #4827: I use Lo-Ko Performance Coatings in Illinois. Cheaper than HPC or Jet-Hot, better sheen appearance, and MUCH quicker turnaround time.

You are all welcome! :D
 
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houstonT said:
Anything you can do to retain heat and keep underhood temps down is a good thing. I would DEFINATELY coat the header. Use Jet Hot 2000, that shit will never come off....
Peter
p.s. expanding of a stainless steal .25 inch thick header? No chance guys, 1600 F is not enough make it expand in such a way that it will crack the coating. The 1600 is cracking b/c it can only withstand around 1600 F and he has hit more than that...
Now I don't feel so bad. I got the JetHot 2000. And the inside has a very thin coat. Supposedly it's guaranteed not to crack, and if it does, they'll recoat them.
 

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maao - i was talking about the OUTSIDE being coated, NOT the inside. I would NOT coat the inside though, that is asking for trouble although the 2000 still "should" not crack...
Peter
 

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I surely agree with not coating the inside of the exhaust manifold pipes.

However I think there is a pretty good chance that most any fabricated (by that I mean welded up of many pieces) exhaust manifold will end up cracking over time.

FYRARMS you sound like you have a lot of experience in this field. Have you found it to be true or not that a manifold that has been fabricated from many pieces and welded up will crack after extended use, especially a manifold that is bringing together 6 exhaust ports into one outlet and has lots of tight bends and not much room to do all of that bending? I would be very interested in hearing your experiences or anyone else's on this subject.
 
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Most exhaust manifold/header manufacturers warranties are voided if the unit gets wrapped or coated. Given that GReddy kits come with no warranty, I wouldn't really care, and would at least use a header wrap on it. This particular manifold is very hard to manually wrap tho, as I did it personally on my car (runners very close together). But, the resulting difference in underhood temperatures is tremendous. Also, you wouldn't believe how close the lower compressor side silicone hose adapter sits to the one of the runners, they are almost touching. I dont see stainless steel cracking, as that surface rather "forges" under extreme heat, rather than falling apart. Ask anyone who ever tried to fabricate a stainless steel exhaust manifold - one welding mistake with too much heat applied, and the newly forged piece needs to be cut off (and forged metal is VERY hard to cut). Most Supras with this manifold would never see over 700-750 rwhp, and as long as the car is tuned right, temperatures should never skyrocket so high causing that the exhaust manifold cracks open.

Exhaust heat wrap ($50)
Coating (depends, approx $150-250)

Its up to you.
 

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93dawg said:
Have you found it to be true or not that a manifold that has been fabricated from many pieces and welded up will crack after extended use, especially a manifold that is bringing together 6 exhaust ports into one outlet and has lots of tight bends and not much room to do all of that bending?
Jim, there are actually a couple of factors involved...

a) Material used.

b) Location of welds on manifold.

c) Type of welding used.

d) Skill of welder/fabricator.

My old employer has been fabricating turbo manifolds/headers since 1988. The welder that works for him is a certified welder who used to fabricate NHRA Top Fuel funny car chassis'. In spite of their credentials, they STILL have some manifolds crack! It has a lot more to do with trial-and-error than people think. It is virtually impossible to predict whether or not you will see cracks. Most cracks that do appear are in a V-shaped joint, such as those commonly found in most Supra turbo manifolds. We had great experience using SCH40 T-shaped pipe sections, TIG-welding them, and then sending them out to be ceramic-coated. Our shop Turbo Neon went 9.80's using this type of manifold with NO cracking. Based on my experience, the BEST way to prevent cracks is to manufacture a log-type manifold such as this (excuse shitty drawing):
 
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houstonT said:
maao - i was talking about the OUTSIDE being coated, NOT the inside. I would NOT coat the inside though, that is asking for trouble although the 2000 still "should" not crack...
Peter
Jet-Hot coats the inside of the header with a 1mm layer of the stuff. Hopefully, if it does start to flake off, it won't be enough material to cause any problems (unless a large chunk happens to fly off!).

But, it's water under the bridge now. I just hope nothing comes of it. If my turbo dies due to the inside coating, I'll just have to upgrade the turbo to a larger one! :D
 

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FYRARMS said:

Jim, there are actually a couple of factors involved...

a) Material used.

b) Location of welds on manifold.

c) Type of welding used.

d) Skill of welder/fabricator.

My old employer has been fabricating turbo manifolds/headers since 1988. The welder that works for him is a certified welder who used to fabricate NHRA Top Fuel funny car chassis'. In spite of their credentials, they STILL have some manifolds crack! It has a lot more to do with trial-and-error than people think. It is virtually impossible to predict whether or not you will see cracks. Most cracks that do appear are in a V-shaped joint, such as those commonly found in most Supra turbo manifolds. We had great experience using SCH40 T-shaped pipe sections, TIG-welding them, and then sending them out to be ceramic-coated. Our shop Turbo Neon went 9.80's using this type of manifold with NO cracking. Based on my experience, the BEST way to prevent cracks is to manufacture a log-type manifold such as this (excuse shitty drawing):
Whoa! amazing drawing :D

J/J... you have a lot of great info there... would you guys recommend coating a cast manifold too... seems like it would be less expensive too right, since its smaller?... I have no idea where to go to get mine coated, not sure if there are any local places or not... I can get it ceramic coated when I buy it, will that make any real temperature differences or just look nicer?
 

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Yep, we coat cast pieces also...

Thanks for the compliment on my drawing. You still have me beat with this pic you did for me when you were drunk:allcho:
 

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Monster, good post, however, you are missing a few points. For one, ppl that run the T88 WILL and DO make 800+ rwhp on this manifold. Also, and more importantly, ultimately it does NOT matter how much power you are pushing, it is more a function of heat, which is a function of a/f. You can push 1000 rwhp through it as long as you are getting enough fuel to keep temps down.
Guys, coat your exhaust manifolds, trust me, it is worth it. You will reduce underhood temps. greatly. Also, the welds on the greddy, hks, and even RPS manifold RARELY let go. It is not really something to worry bout...
Peter
 

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If you are worried about fatigue failures, get the header vibratory stress relieved. This method has shown great success in minimizing residual stress in weldments, which is a major cause of stress fatigue fractures. This is what I plan to do after I finish making the header for my MKIII.
 
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turbotoy said:
If you are worried about fatigue failures, get the header vibratory stress relieved. This method has shown great success in minimizing residual stress in weldments, which is a major cause of stress fatigue fractures. This is what I plan to do after I finish making the header for my MKIII.
Correct. Also, many exhaust manifold crackings are caused by engine twisting under load and turbo being pressed against passenger side shock tower, thus putting torsional stress onto welds.

houstonT, i forgot about T88, you're right. It all comes down to how well the motor is tuned, air/fuel, and exhaust temperatures should never get out of hand.
 
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