Funny how the EPA gets the blame for everything that doesn’t work. Porcelain manifolds have NEVER been durable.
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That’s kind of what I’ve thought. If the original process was so durable, you’d think there would be some intact or presentable examples floating around. There are still enough survivor XK engined cars to expect a few driven samples to still exist.
Dave
They danged sure used to be more durable.
I had new porcelain manifolds fitted. Porcelain was coming off before I even picked up the car.
Porcelain is super durable and cast iron isn’t flimsy, but getting the two hard, rigid materials with different coefficients of expansion to adhere to one another over large areas at high temperatures is next to impossible. Once the cracking and separation starts where the flames impinge on the outer curve, some of the strain is relieved and small areas may stick indefinitely. Other areas like the head flanges that never get super hot practically never lose the porcelain. Anyone with pristine manifolds either has not driven long enough at high enough revs, or has rich mixture, or has found the Holy Grail - in that order.
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Wasn’t Jaguar the kind of company that only needed those manifolds to look shiny and pretty until the car was sold and off the showroom floor?
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I have also been on this forum a long time, and seem to recall the chemical in question was cyanide, (possibly as a by-product ?)…I have manifolds over 60yrs old with ok porcelain, anything after the '70s is rust.
It may be possible that cyanide was not involved, but porcelain does seem to last a lot less now than it did originally, based on my old manifolds.
Last I checked, (which was years ago), Zircotec had withdrawn their gloss black, due to failures
(specifically on E-types)
Thanks Tony, you’ve reminded me of what the owner of the porcelain shop told me when he re-porcelained my manifolds. Cyanide was part of the pre-treatment process for the proper application of the porcelain (along with a bunch of other noxious chemicals).
And, looks like the EPA does take the blame for ending its use after the RCRA Act of 1976 governing hazardous waste.
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So do you want some cyanide to make your Jaguar perfect or are ya good?
I have restored a couple of XK120 and XK140, where the original porcelain was still intact and looking rather good. On the E-Types the porcelain usually gone away. My guess its the higher compression and more power on later cars is the reason.
I have an xk150 with equally nice porcelain. The etype runs a lot hotter. Porcelain doesn’t stand a chance…
Maybe porcelain on Etype manifolds are more likely to fail than on XK manifolds because of the E-type’s louvers, which cause them to be doused with rain water while hot. Wonder if E-type manifolds do better in desert conditions.
My etype manifold porcelain failures had nothing to do with water. I am a proud master of not learning from other’s mistakes. All are welcome to waste $800 on some nice porcelain ones like I did. Would work fine if only going from the trailer to the Concours show site. After the breakin period, a couple hours straight at highway speeds is all it took for mine to craze and start to flake off.Its all about differential thermal expansion between cast iron and porcelain. Cast iron grows fast, porcelain, not so much. Might be worth a try if you can get a warranty with a new set.
I think it’s the other way around. Cast iron has a CTE around 5 to 6x10-6, while kaolin-based ceramics (i.e. porcelain) are around 15 to 18x10-6.
Brush them up as best you can with a wire brush, then apply a manifold dressing like Calyx or Hot Stuff, available from Eastwood or Amazon. These coatings seem to be waxes with metallic particles mixed in. When you run the car, the wax burns off and leaves a coating of metal flakes. It’ looks like raw cast iron if you don’t look too closely. Won’t last long, but it’s about as easy to reapply as shoe polish.
If you look in Marks Engineering handbook, cast iron grows at twice the rate of porcelain. Chapter 4, table 12, eighth edition. Anyway it flakes off the cast iron as it cools back down. MOX Nix. It’s destined to fail.
I used to use stove black, on deporcelainized ones.
Would POR-15 work? It’s tough stuff, but I dunno what temp it’s good for.
POR-15 is a moisture-cured urethane paint. I’d be surprised if it could endure more than 300°F for more than a few minutes.
Dave
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