Exhaust Valve Stem Seals (Revisited)

Sometime back we had a rather lengthy thread on here which I started, inquiring about the issue of whether the AJ6 engine has seals on the exhaust valve stems or not. As I have mentioned several times before, Superblue has her “blue smoke” issue briefly upon first start up in the a.m.s (well, most of them). :angry: We couldn’t seem to reach a definite consensus on here as to whether the AJ6s have them or not. :confused:

I believe I finally have found the definitive answer to the question, and it would explain why they were both yeas and nays on the issue earlier. Per p. 22 of the current hardcopy issue of the Moss Classic Jaguar parts catalogue (a pretty good source for XJS parts, too, btw :wink:), Jag apparently started out with NO exhaust stem seals on the AJ6 engine, but switched over to include them, beginning with engine # 163523.

Query, does anyone know in which MY Jag went to that # engine? Alternatively, where is the engine # located on our AJ6 engines (and hopefully I won’t have to get underneath the car to check it :blush:)?

If you ever discover what your valve stem seal situation is let me know.
Get the measurements and send them to me.
I have hundreds of NEW seals that were never installed by the shop I worked at.
They are in sealed bags and offered for the cost of postage.
Since I don’t have my XJSs I don’t visit the forums as often so Call or text.
Steve @ 650-455-1110

I too have bags of these seals somewhere in my shop from working at the dealer for years.
I sent a few dozen to the guy that built the MEDUSA twin Jaguar AJ6 engine car.
I think I still have some in ‘partial’ head gasket sets on a shelf.

Thanks, Equip … may take you up on that. One thing is I would need access to a full shop that has an air compressor, in order to avail myself of that “air pressure shortcut” to be able to r/r the exhaust stem seals relatively easily w/o having to pull the cylinder head, etc… :+1:

btw, to answer my own question, I did find a very helpful photo of the location of the engine #s on the 4.0s on the XJS registration website. It is stamped across an area of the engine just “northwest” of the distributor, when facing it from the passenger (LHD) side fender. Had to clean a bit of grime off it, and after a many-letter prefix, it appears to be a 195xxx #. I’m thinking that, unless Jag made a heck of a lot of 4.0s in '94, then the inclusion of exhaust valve stem seals likely began sometime in the '93 MY, or possibly even during '92. :thinking: Of course, that also means Superblue must have come with them, and they just eventually deteriorated and lost their “seal” over 25 or so years. :frowning_face:

Thanks, too, motordude. btw, ltns. Glad you are O.K. over on the other side of DFW. Look out, we’re supposed to have SNOW tomorrow! :snowflake:

My '94 XJS 4.0 was built on Mar 24, 1994 and has engine # 193902, so it would seem Jag must have made the switch in the 1993 MY? My car as the same problem, blows blue smoke at start up when it’s sat for a while. Do you know if new seals can be replaced w/o removing the cylinder head?

Fortunately, yes, if you know of a tech who is familiar with the “short cut” route and willing to go/risk it. :grimacing: Basically, involves using compressed air through the spark plug holes to keep the corresponding exhaust valve “up” (closed) while the retainer and its split keeper are removed, one at a time, the valve seal r/red, and then the retainer and split keeper reinstalled. :+1: If something happens to the compressed air pressure in the cylinder though during the process while the split keeper is removed (e.g. air compressor fails or gets unplugged/loses power) - "Houston, we have a problem … " :open_mouth:

There are other ways. One member gave us a colorful description of winding a bit of rope into a spark plug hole and then turning the crank around until the piston pushes the rope up against the valves to hold them in place.

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Beat me to it Kirby I was going to post that option as well.

Done that a few times on Chevys with broken valve springs.

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That method kind of scares me, too … What if the rope gets “caught” in there, or a piece breaks off inside? :grimacing:


This method was one of the first things I have seen when I was a kid. Most of the workshops were doing it. Even if they’ve charged you for full work involved. It’s a working hack, not the way to trash your engine…