Porcelain repair

I wonder if it could be a case of EPA type regulations being relaxed lately. I know years ago when I got my manifolds re-porcelained by a local company, the owner warned me it wouldn’t last because they weren’t able to use certain ingredients any more.

They looked gorgeous at first but cracked up after about a year. In comparison, I once had an 50,000 mile XK150 which still had perfect porcelain on the original Jaguar manifolds.

I’ve been on this forum over 20 years and never heard before that anyone can successfully replicate the original porcelain, so what’s changed?

1 Like

Yes I’m gonna try that. Next winter’s project.


I think his contention was that there is a difference between something made entirely of a certain type of silicon and a paint or other topical covering that has silicon in it. He read from the safety data sheets that come with his paints, and other hot applied coverings which specifically said not to use it near food.

Silicon and silicone are like apples and oranges. Silicon and it’s normal form, silica may be an inhalation hazard like asbestos.

I can’t be sure but I think I remember that Prairie also coated the internal passages with ceramic material. They also suggested running with a richer vs lean mixtures.

That would cool the exhaust but also seems like a bodge. Ideally, the materials should accommodate the proper mixture, not the other way around.

I smoothed my manifolds using Roloc 3" sanding discs in 36 and 80 grits and coated them at home with CereKote. After a few thousand miles and 16 months they still look like they did when I first coated them. I bought the bare, uncoated manifolds from one of the usuals; SNG IIRC.


I wasted $800 on a “new” porcelain set from the usuals. After break in period, most of it just crazed and flaked off like shards of glass. Under the flaked porcelain was a very rough and rusted surface. The surface prep was just total crap. Looked like typical Chinese product sans 24 hour QA oversight. I ground and sanded my original manifolds and sent to Jet Hot. I miss the shine but the durable matte black finish looks much better than than rust.

I sandlblasted mine and then sprayed with Tremclad 2000. Then baked in oven as per instructions.

It went on black but then cured to a gray with the heat.

Has been wearing well for perhaps four years now

Dennis 69 OTS

Funny how the EPA gets the blame for everything that doesn’t work. Porcelain manifolds have NEVER been durable.


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.


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.


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?

1 Like

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.

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.