Re: [xj-s] Valve Stem Seals

["David Low" <dkl@lbwf.gov.uk>]

Hi,

have been following this trail with some interest, but have become a bit
alarmed in one respect.

The Jaguar engines, from the outset were designed to be relatively 'loose',
and always burned/used/consumed some oil.

If you start reducing the oil feed to stems, especially exhaust valves, you
are going to cause localised overheating. Other items in this newsgroup
indicate to me that overheating appears to be a real problem in the USA.

If you overheat a valve at the stem/guide interface, you will at best
increase wear rate, and at worst cause a local siezure, possibly with the
result of dropping a valve guide.

If I was to contemplate doing this on either the AJ6, or any of the V12
variants, I would be looking very carefully at the actual valve
composition, and the engineering profile.

Without research, I'm not sure of the type of valves fitted, but would be
looking for sodium filled, and stellite faced valves. I would consider
teflon on input valves.

Before any of you actually undertake this process, I strongly recommend
that you contact either AJ enginnering or TWR (Tom Walkinshaw Racing),
contactable via the JagWeb. These engineers have probably the widest
experience of Jag engines.

The original nitrile seals do wear, and are known to be a problem, and they
also get brittle, again overheating?. However we have few problems here in
the UK, and I'm sure the lower ambient temperatures must part of the
reason.

As the temperatures in the USA are very high this year, I would also try
and find out what specs Jag used on engines shipped to the middle east..
Probably lower compression ratios, different radiators, high capacity water
pumps etc etc....

regards

David L


----------
> From: Michel Carpentier <carpenti@math.jussieu.fr>
> To: palmk@mailer.gadcomm.net
> Cc: xj-s@jag-lovers.org
> Subject: [xj-s] Valve Stem Seals
> Date: 27 July 1998 09:12
> 
> >From: "Kirbert" <palmk@mailer.gadcomm.net>
> 
> >Boy, THAT was easy!  24 Teflon valve stem seals on order, 75 cents 
> >each.
> 
> 
> 
> Glad it was easy for you ! 
> A few tips for installing them. You cannot push them in as you would
plain
> vanilla seals. With your package you should get a clear and rather flimsy
> plastic tube closed at one end. Slipped over the valve stem, it protects
> the seal as you first push it over the stem end (push with your thumb
with
> a slight rocking motion to get started)  then slide it over the cotter
> groove. Trim this sleeve so it still covers the groove but does not stay
> trapped under the seal when fully home.
>  When you start, remember (24 times!) to put the spring seat first as it
> does not fit over the seal. This is especially important as a teflon seal
> cannot be removed without being destroyed: 1) it is hard to pull it from
> the guide without distorting it and 2)as it goes back over the cotter
> groove, the sealing surface between stem and seal will be damaged.
> Now you need to push the seal over the guide. Use a tube (e.g. a deep
> socket) with ID greater than the narrow upper section and a rubber
mallet.
> A first blow will get you over the guide chanfer, then tap it all the way
> in. Don't hammer too hard though or the upper portion will shear off as
you
> hit bottom.
> Cheers.
> 
> Michel Carpentier

---

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