I wish I had known that before, I got the grill over 500F , fortunately without ill effect. This was just a practice run anyway on the cracked header I had
If there’s any cracks it will be the end of the manifold.
Sorry I didn’t say anything about the temperature. I guess it didn’t catch fire. Good for you! Manifolds get well over 500F on the car as I think frank said. I don’t know about glowing hot – that I haven’t witnessed.
Send pictures when you get a chance
It didnt come out great, to be honest but i was kind of expecting it since my header was either corroded or dirty and I figured i hadnt put enough ATF on it.
I sent you a PM because JL forum said so. anyway, hit it with a wire brush lightly and see if it looks any better send us pictures.
Good one about the steaks… that made me chuckle. thank you I needed that
the graphite is a snap. just spray it on, wait over night to dry then install it. if a bit comes off then just spray it on the car… I mean after the manifold is installed, you can touch up spots that have rubbed thin. It won’t darken anymore meaning it blends very well with existing coatings of graphite. touch up just shoot it on the car and cover areas you don’t want covered. The stuff wipes off really easily too. but it’s really hard got get out of cracks where your don’t want it.
While that may reduce radiated heat, Mark - it will certainly increase manifold metal temps. Which is nothing to aim for…
xj6 85 Sov Europe (UK/NZ)
Ahh if anything you should have done a very light coating on an already hot manifold in my opinion that would work best. I’m glad your kids still talk with you
Hi David I haven’t really done anything to the 2 headers going back on the car yet except sandblasting, I was just experimenting with the cracked one.
Please describe exactly how you would do it.
So far I have a bbq grill, 2 headers and atf.
Frank JetHot just came back with a quote of $318 for their coating which supposedly reduces temps by 50% and has a lifetime warranty but your comment suggests that it would actually be bad for the headers. You dont think they can take it? I’m moving the car to Florida with me so operating temperatures would be high enough already
who else is of that opinion?
I’ve not actually seen an independent confirmation of those drops in temperature, but I believe there has been a few anecdotal reports, that Jet Hot really does do that.
I happen to think it’s probably the best alternative for coating exhaust manifolds.
Let’s just assume the product indeed performs as advertised and i’m willing to spend the money in the name of curiosity and “research”, could it actually be bad for the headers due to their metallurgy like frank suggested? could their internal temp get higher increasing the odds of having cracked headers again?
No: many thousands of headers have been JetHotted, and it’s a well-developed process.
Search the archives for numerous photos of it.
I‘m not qualified since I‘ve never done it with atf, but what I would do is get the iron to temperature (so the oil polymerizes before evaporating) and then I‘d use something like steel wool to brush on several light coats. Soaking the headers in oil is too much.
I would never put anything expensive or messy on there, just do what the factory did and leave it alone. There’s no real benefit in obsessing about the exhaust manifolds too much!
If we had jet hot in the UK , I’d jump at it . There is something similar here , about £700 , and not the colour range . Not an option
OK folks I have decided to splurge and send Betty’s headers to Jet Hot. Is it needed? probably not, like David said but after 3 other xj6’s and a xjs she’s been rock solid until now so, I’ll spend a lil bit on her.
I’ll report when I get them back which should be in about 3-4 weeks.
Thank you all again for your input on that matter,I learned a ton.
@Frank_Andersen on cast iron you are absolutely correct. that’s why I said
The heat is generated from hot gasses inside, Francois - and can only be dissipated by external radiation and heat transfer to other parts. If the promised temp reduction is true, it can only be by increased radiation. The shields are there to protect the surroundings - they, arguably, do nothing positive for the headers. There are no free lunches in physics…
Honestly; billions of headers are has been subjected to engine generated heat over the years - with few failures; they are made to stand it, ‘naked’ or coated. Basically; coatings are for appearances - and is, within reason, at worst harmless.
xj6 85 Sov Europe (UK/NZ)
As I understand it, Jet-Hot coats the inside and outside. The inside coating insulates the manifold from the hot gases somewhat, meaning those gases remain hotter as they move on down the exhaust system. The insulating coating on both inside and outside the manifold reduces heat into the engine compartment, reducing the temps in there.
That’s fair enough, Kirbert - and will certainly improve flow, but hot the headers will still be…
xj6 85 Sov Europe (UK/NZ)
I don’t know about applying Jet-hot to cast iron exhaust manifolds, but on the headers on my GPmoto bike, it lasted about a season before it burned off. it’s all about expansion rate differentials. with my stainless headers on the motorcycle, it started flaking off after the 3rd month of racing.
and not to be debbie downer, but I haven’t seen a ceramic coating that’s stayed on an XK exhaust manifold for long.
I’d be curious to see how well the jet-hot works on cast iron.