exhaust manifold

Another thought... Some of todays powdercoatings can take some serious heat... not sure if manifold heat is too hot.. I would think it would be, but others tell me different.

1969 Jaguar E-type

Bill,

Interesting observations re: the porcelain. Virtually every re-porcelained set of manifolds I've seen start to show signs of pitting and discoloration once the car is driven any significant amount of time. I've heard the comment before that deterioration is hastened by bad timing or other tuning issues leading to excess heat in the manifolds. Kills the exhaust systems too and produces complaints of excess heat in the footwells also.

I'm going to file that name away for future reference. I was going to Jet-Hot my manifolds this winter, but if these guys do a really good job with the porcelain, I might give that some thought.

Regards,
Steve Weinstein, JTC-NJ
'72 E-type 2+2
'70 XKE FHC

Our local Jaguar drivers Club had their monthly get together at my shop in Los Angeles last week. One of the items discused was finishing of manifolds and one member brought along a sample of a one which had been finished in a white coating which apparently is supposed to be "long" lasting. The original porcelain used on your manifold was excellent. There are many cars around of all types which still have the original finish, Coincidentally, a member had brought along his,never painted, original engined, original carpet 120 OTS. Guess what? the manifolds were in good shape, not glistening black, but not cracked. Today we have in a 69 E on which we rebuilt the engine and re did the manifolds in 1984, they are still good! Due to environmental regulations it has become increasingly difficult to get good porcelain. The only shop I know off who still does it correctly is Prairie Auto Porcelain in Northfield Minnesota. tel 507 645 0987. They take up to 2 months to do the job but it is worth the wait. if we are doing a job and don't have a shelf set the very first thing we do is send them the manifolds. We prepare them by repairing/replacing the studs first. The reason that most finishes crack is due to excess heat, this is caused mainly by bad ignition timing,(too retarded)or a weak mixture. Both of these conditions lead to an incomplete combustion process which means the mixture is still burning and expanding as it enters the manifold. I have seen cars where the paint on the bonnet has started to blister and crack due to the tremendous heat. Good luck.

Jaguar affectionado and etc.

Bob,

What you describe is typical of porcelain manifolds. There is virtually no way of avoiding it short of not starting the engine once you install the nice shinny new manifold. The heat generated by the engine will cause the porcelain to pit, not matter what you do.

There are alternate coatings out there. Some people like a coating called Jet-Hot (can be found via an internet search). The problem with most of these coatings is that they do not look like porcelain, although they do hold up much better. So if you are restoring or maintaining a concours car, you won't have the look of porcelain. If it's just a driver and you are looking for a good coating that will hold up, check out Jet-Hot. NAYYY.

Steve Weinstein, JTC-NJ
'72 E-type 2+2
'70 XKE FHC