Exhaust manifolds / headers.

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Hugo
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#1 Exhaust manifolds / headers.

Post by Hugo » Thu Mar 15, 2018 10:45 pm

What is the best way to deal with the exhaust manifolds/headers? I can buy new ceramic-coated headers quite cheaply, but I have heard that the coating probably won't last long. My originals have lost all their coating and have a finish of surface rust over the rough cast finish.
Jet-Hot in N. Carolina do some impressive looking coatings, but the one thing they don't do is gloss black.
Is there anything approaching a consensus on the best way forward?
I believe stainless headers might sound 'tinny'?
Hugo Miller - rebuilding an imported Series II OTS & converting to RHD

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chrisfell
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#2 Re: Exhaust manifolds / headers.

Post by chrisfell » Fri Mar 16, 2018 6:50 am

Hugo,
When mine lost their porcelain coating, a process that took about three cold starts to commence and less than one year to complete, I painted them with VHT exhaust paint. They get a fresh coat every three or four years, or 15,000 miles or so. I have no intention of decoating them with anything, but one day they might be replaced with stainless steel tubular headers (with matching cam and breathing mods) - much better looking.
Chris '67 S1 2+2

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#3 Re: Exhaust manifolds / headers.

Post by christopher storey » Fri Mar 16, 2018 9:17 am

Like Chris Fell, I use Halford's motorcycle paint on an annual or thereabouts basis, and they look quite respectable . The ceramic coating was a lovely idea but does not last, and as you say SS produces unwanted combustion noise easily heard as a tinkling sound, and also the 6 branch type tend to produce a hole in the torque curve at about 2500 - 2750 rpm which does not matter for racing but which spoils the mid-range on a road car

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#4 Re: Exhaust manifolds / headers.

Post by Mark Gordon » Fri Mar 16, 2018 11:39 am

+1 on VHT. It's cheap (a $10 rattle can will do the job with plenty left over for later touchups PRN), lasts quite a long time (2-3 years before touchup is needed) and once cured the "flat black" finish can be buffed to a semigloss type shine. It won't do for concours, but if you're looking to make your cast iron manifolds presentable, I think it does the job.
Mark

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#5 Re: Exhaust manifolds / headers.

Post by alfazagato » Fri Mar 16, 2018 12:25 pm

My stainless system neither tinkles nor has a flat sport.....what am I doing wrong?

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#6 Re: Exhaust manifolds / headers.

Post by christopher storey » Fri Mar 16, 2018 12:39 pm

Are you talking about a stainless exhaust system, or about a stainless 6 branch manifold ? The system itself is fine, if a little less mellow than a mild steel system, but the manifolds almost universally create the problems I have described. A number of people have produced threads on this forum with rolling road testing which illustrates the alteration of the torque curve .

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#7 Re: Exhaust manifolds / headers.

Post by 64etype » Fri Mar 16, 2018 12:57 pm

Jet Hot is ceramic. It does not peel off like porcelain. The offerings by suppliers is presumably the same as Jet Hot. As far as I know it is only available in semi-gloss or flat for the color black. I am a big fan of this coating (for heat control and rust prevention) and had the entire exhaust system coated by a local company that protects materials for underwater offshore oil rigs. You could do the same with your existing manifolds or buy the products from the suppliers (this was not an option back when I had mine coated). I have used ceramic on headers and down pipes for may years with excellent results.


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#8 Re: Exhaust manifolds / headers.

Post by Hugo » Fri Mar 16, 2018 2:41 pm

In my ignorance, I thought porcelain and ceramic were the same. Not my field really, the only thing I know about porcelain is that is derived from a very rude Italian word describing the anatomy of lady pigs (apparently it comes from a shell that bears a resemblance to, er, female porcines). That's the Italians for you I guess.
One option that I'd like to investigate is the possibility of Jet-hotting it to reduce the external temperature, then sticking a gloss-black coating as per original over the top.
Does anybody do the gloss black coating? Would that work?
Hugo Miller - rebuilding an imported Series II OTS & converting to RHD

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#9 Re: Exhaust manifolds / headers.

Post by Hugo » Fri Mar 16, 2018 3:51 pm

christopher storey wrote:.......... and also the 6 branch type tend to produce a hole in the torque curve at about 2500 - 2750 rpm which does not matter for racing but which spoils the mid-range on a road car
Then, just to confuse the issue further, I read this on Classic Fabs website (regarding their stainless long-branch manifold); "An increase in power of around 5 to 10% can be achieved in the mid range (2500 – 3500 rpm), which gives the engine a stronger torque curve."

Any comments?
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#10 Re: Exhaust manifolds / headers.

Post by 64etype » Fri Mar 16, 2018 4:06 pm

As far as I know no one offers gloss black in ceramic. One company was advertising it a couple of years ago, but apparently it didn't work. If you paint over the ceramic, the paint will eventually deteriorate just like it does when applied directly. I wouldn't attempt it. And if you're considering headers...not original...why would you care if the ceramic is slightly less than gloss finish. At least it isn't flaking off and allowing rust to form.

Yes, the ceramic cuts down underhood temperature...a lot in my experience. I'm hoping for some relief under the car as well. All part of my war on heat transfer.

The engine already has gobs of torque for street driving. Unless you're competing in some sort of race event or the stop light Gran Prix, it won't matter.
Eric

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#11 Re: Exhaust manifolds / headers.

Post by Hugo » Fri Mar 16, 2018 6:52 pm

Sorry, let me clarify; what I would LIKE is the original gloss back on my original cast headers. But I want it to stay on. I can buy new ones quite cheaply, but I think the chances of the black ceramic staying on there and intact for any length of time is remote.
But that does mean that SOMEBODY is doing the original-style black coating.
I might consider s/s as an alternative, in which case I would just leave them 'au naturelle'.
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#12 Re: Exhaust manifolds / headers.

Post by Heuer » Fri Mar 16, 2018 7:03 pm

No one can provide a gloss finish coating that will stay on the manifolds. They usually last about 1,000 miles or until the first time you are caught in the rain. The right hand (rear) manifold is the most susceptible to coating loss probably because it is under the louvres. When you apply the brakes in the rain, water rushes forward from the windscreen and goes through the louvres straight on to the hot shiny coating causing it to craze and flake off. Best finish by far is BBQ paint from B&Q and not as expensive as stuff like VHT.
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#13 Re: Exhaust manifolds / headers.

Post by Hugo » Fri Mar 16, 2018 7:21 pm

Ah, but if I could reduce the external temperature of the manifold by 'jet-hotting' it first, the gloss black coating might stand a better chance don't you think? If it will stick. And if I can find somebody to do it.
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#14 Re: Exhaust manifolds / headers.

Post by timhum » Fri Mar 16, 2018 9:42 pm

There's been a lot of correspondence on the TR Register forum about the claims made for ceramic coatings reducing under bonnet temperatures. The consensus after various tests, although not particularly scientific, is that they make no appreciable difference. Visually they are quite good but that's about the only benefit.

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#15 Re: Exhaust manifolds / headers.

Post by Series1 Stu » Sat Mar 17, 2018 12:08 am

I'm struggling to believe that any form of coating on an exhaust manifold would reduce under bonnet temperatures by any significant amount. Especially in a conventional road car configuration.

I do hate the sight of a rusty manifold though. So from that point of view I am in favour of such things.

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#16 Re: Exhaust manifolds / headers.

Post by Mark Gordon » Sat Mar 17, 2018 12:14 am

Heuer wrote:
Fri Mar 16, 2018 7:03 pm
Best finish by far is BBQ paint from B&Q and not as expensive as stuff like VHT.
Huh? VHT is $9.49 at my FLAPS. How much is a can of BBQ paint? Do they give it away for free? :bigrin:
Mark

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#17 Re: Exhaust manifolds / headers.

Post by Series1 Stu » Sat Mar 17, 2018 12:21 am

About the same.

Although that reminds me that I still have some high temperature paint left over from doing my stove pipes....
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#18 Re: Exhaust manifolds / headers.

Post by daykrolik » Sat Mar 17, 2018 12:24 am

This question has been much debated. Not one to eschew controversy, I'll put in a word for the original gloss porcelain look, which is not only original but distinctively beautiful. I owned an XK 150 from 1964 to 2012, drove it hard and put many miles on it. The original porcelain manifolds, for me, lasted up to 10 years and 40,000 miles (I had three sets). I realize there is an issue with louvers and rain on E Types. I also have a suspicion that the original porcelain process has been somehow lost in time and become a victim of more stringent environmental standards. On my E, the porcelain manifolds now last about three years and I replace them. I fully realize there are more economical alternatives. I just keep hoping that, rather than surrendering to a less desirable alternative, we can search for and/or push suppliers to produce porcelain manifolds, like the originals, which will last a reasonable period of time.

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#19 Re: Exhaust manifolds / headers.

Post by Hugo » Sat Mar 17, 2018 12:58 am

Series1 Stu wrote:
Sat Mar 17, 2018 12:08 am
I'm struggling to believe that any form of coating on an exhaust manifold would reduce under bonnet temperatures by any significant amount. Especially in a conventional road car configuration.
Oh I dunno - it makes sense to me - the thing about the Jet-hot process is that they coat the inside as well as the outside; if you use a reflective silver coating it will work like a Thermos flask & the heat will go out the taipipes. Black would of course be less effective, but they claim it still makes a significant difference.
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#20 Re: Exhaust manifolds / headers.

Post by 64etype » Sat Mar 17, 2018 1:31 am

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