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MG MGB Technical - How Hot Does The Exhaust Manifold Get?

I am installing a used exhaust manifold on my "B" and was thinking about cleaning it up and painting it prior to installation. I see a lot of "Hig Heat" paints on the market, most listed at around 500 degrees farenhite. How hot does the exhaust manifold get? Will a GOOD 500 degree paint work?

Thanks,
DT
Danny T.

we coated the manifold (inside and out) with a ceramic coating. i understand that it not only rustproofs the metal but helps with something called "scavenging" -

see www.jet-hot.com/

rn
RN Lipow

I believe that ceramic coating is not good for all types of manifold (mild, stainless and cast iron). I don't know which ones it is good for, but I'm sure someone will.

Iain
I D Cameron

Danny,

No it will not. Under some conditions an exhaust manifold will glow dull red. This would be in the 1200-1400 degree range. So normally expect it to see 1000 degrees or so.

Jim
Jim Blackwood

Iain-
Why do you feel that ceramic coating an exhaust manifold is a bad idea? I had my exhaust manifold Jet-Hot coated and the results have been excellent. The heat will have nowhere to go except out through the exhaust system, thus it will greatly reduce underhood temperatures. The biggest advantage of this is that the air being inhaled into the engine being denser, more fuel can be mixed with it to result in a more powerful fuel/air charge. Another benefit is that the setting of heat-sensitive SU HIF4 carburetors can remain more consistent. One word of warning to those considering ceramic coating: Be sure that the entire surface of the manifold, both the interior as well as the exterior of the manifold and that of the flanges, is coated so that the heat of the exhaust gases will pass on through the system instead of being absorbed and trapped in the metal of the manifold, otherwise the manifold will create the same problems as in the case of wrapping the manifold with insulating wrap. So long as it's done properly, I can't think of a single disadvantage.
Steve S.

Eastwood *may* have a header paint. I would only trust ceramic coatings like jet-hot. If it doesn't say "for exhaust headers" then don't get your hopes up.

Anders
Anders Green

Danny. On a properly tuned engine, the header/exhaust manifold runs something less than 400 deg F. This is an actual, measured temperature, taken using an IR thermometer and readings taken with several vehicles and averaged. The 500 deg F paint will work fine, but will discolor over the years. Ceramic coating is probably better, but costs a lot more and the parts have to be sent out. Painting will work fine for most applications. Les
Les Bengtson

Danny. Go to techlinecoatings.com I have used there ceramic coating on both cast iron manifold and mild steel headers. It worked great both times. I plan to coat the complete exhaust system next spring.Bob

ps. It goes on easy with touch up gun.
Robert Novak

Robert. Thanks for the tip on the website. Something that can be applied at home is always useful. But, for any coating to stick to the metal properly, the entire surface must be clean and rust free. This may be beyond the capablility of many hobbyists. For small parts, I use beadblasting, followed by a through cleaning with hot, soapy water and blow the parts dry with compressed air. Then, coat immediately. This becomes more of a problem with large parts. With the PECO header, I used paint stripper to get the cheap paint off, washed the part throughly, then painted using a "header paint" from Checker. It seems to be holding up fairly well, but the paint seems to be of the type which has to heat cure. Use rubber gloves when installing the part(s) to keep the hands clean.

What is your experience with the Techline coating, what did you do to prep the pieces and did any of it tend to rub off when installing the parts? Les
Les Bengtson

Les. I have had very good results with the Techline coating. The only one I have used is black satin but it's as easy to use as they say. It air cures so you don't need a large oven. Also it realy does lower the under hood temp. You have to sand blast the manifold.I use a gravity feed speed blaster from any auto paint store. I have also used a local sand blasting service. Then rinse the part in solvent I used laquer thinner. Then spray a light coat with a touch up gun or air brush. It dries quickly and can be handled in an hour or so. I used it first on my MGA cast iron manifold. It started out old and rusty and ended up looking like new. This fall I coated the headers of the v6 that Iam puting in my B. They turned out good also. I like the stuff so well I plan to coat muffler and pipes in the B next spring. Bob
Robert Novak

Some of the high heat manifold paints have a warning on them saying not for use on european manifolds. I have read somewhere that the reason for that was that the european manifold had a lot more silicon in the castings. I do not know how true this is,but have had a lot of problems with MGA units. The paint would peel off in large chunks.
Sandy Sanders
conrad sanders

Iain,

Coating or wraping (+other probs)the outside of mild on non crossflow like B, may be detrimental to bhp. Steve recommends both inside and outside of mild.

Stainless should not need coating, but can be coated on outside to reduce under bonnet temps.

Paul
Paul Wiley

Bob. Thanks for the tip. I have looked at the website and it looks to be interesting. Since, as soon as I get a rebuilt engine installed in one car, I need to get started on another car, I may be in a position to test out some of these coatings. I have used one form of bake on coating, Gun Kote on clutch master cylinders with excellent success. Perhaps some of the Techline coatings will be worth experimenting with. Les
Les Bengtson

This thread was discussed between 19/12/2003 and 20/12/2003

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