Mike Moore
63 OTS
70 XJ6
SAYS,
So today, I took my 4.2 head to a prominent E-Type mechanic/restorer in the
Bay area to have him send my head out. I asked him to have the machine shop
leave the valve adjustment to me, and to not “top” the valves. He said the
machine shop would not work that way, that topping the valves was the
correct
way to do it, and that’s all anybody did. ( I thought "Why does Jaguar have
30 shim sizes available?)
As a side issue, the same prominent restorer told me he had appeared as an
expert witness against two other shops who had lapped down .085 shims to get
clearance. He said that grinding shims undersize can cause the tappet to hit
on the retainer before it hits the stem and can cause a valve to drop when
the collets pop out. He led me to think that it was sensitive enough that
ANY
grinding down of shims to under .085 was risky.
Terry Says,
To remove Material from the valve stem is OK I do Aston Martins like that.
as well as Jags Aston Martins have no shims, the stem is run straight onto
the Cam Follower.
If a Jag needs to have a bit of clearance because it will not make it’s Min
Clearance Setting I will Grind the Valve Stem on a Valve Re Facing Machine.
The Valve is supplied New so you can do that.
In respect of the Thinner Shims & Cam Follower hitting the Spring Retainer,
that’s nonsense if you look at the mentioned parts, if you measure you will
see what I mean.
Even if the Shim was below the Highest point of the Spring Retainer, that
would not happen. NO HIT.
What would happen if the Valve Stem was Ridiculously too Short above the
Valve Collets is that it would hit,the situation would be so ridiculous that
you would then need a Shim atleast twice as thick as the Max Jag size of
.110".
I don’t like Thin shims for fear of them breaking,however I have not seen a
broken one yet,I have seen plenty of thin shims.
The Jag Valve Springs are very soft and the Cams are very easy in operation
so there is not a lot of thrashing going on.
I don’t use thin Shims, I did when I was a boy because I could not afford
new ones and I did not have facilities when still at School,however after
some rattly Heads, I sort help and got assistance from my Dad’s Mate who had
a Workshop,at that time Dads’s workshop was 1.5 hours from our home, later
on I had full access to all sorts of Gear which made a big difference to my
MK7 M 3.4,I was just 15 and had all sorts of little problems with a Moss Box
pulled to bit’s in my Bedroom, I lost the Balls & Springs from the Synchro
Hubs, that I remember was such a Drama, I got the bit’s required from Frank
Gardners Mobil Garage at Whale Beach, I became friendly with a Young Lady
whose Dad worked for Frank, not nice but I needed the bit’s and there were
so many Jag’s being worked on all over the place it was Heaven, she was
pretty good too.
So the Mk7M got going again and I learnt a lot about G/Box’s and a young
Lady,she accused me of being more interested in Jaguars,I did not realise
that at fifty years of age I would still hear that same tune, all my Mates
with Jags know it too.
Well I did it again, got of the Track,
Mike, I really think that your informant was telling you a mixture of Scare
Tactics, some White Lies, he exaggerated the situation of the Scenario of
too thin shims.
Actually he told more then White Lies, I think he must have been trying to
impress you
the Expert Witness thing sounds like B/S the Defendant must have had a silly
Lawyer or a V/W Expert witness. Too Much If But & Maybe, ask your informant
for the Case number etc, I think he is pulling your leg.
If you run out of shim Range on the Ser1 E type use the XJ6 and or Ser2
Cams,your back in range and have better easier Cams to deal with the setting
Clearance .
The Valve stem is as hard through to the centre as it is on the outside they
are induction hardened, New Valves need to be Ground on the Stems otherwise
the Shim is too high and can in some instances jump out and become lodged
between the Spring Retainers, infact this is a common cause of Dropped
Valves in Jaguar Heads.
Some Brand Valves are longer then others so this depends largely on
theValves being used,remember Jaguar do not make Engine valves for XK
Engines, they never ever did.
Most Engine Valves available for XK Engines are made in India and are better
then what was originally fitted to Jaguars.
Sometimes I use Hardened Top Hats for the Valve Stems, Jaguar Valve Springs
are soft and the Valves do big mileage’s without stem wear of any concern.
Some people replace Valve Seats when Valves become out of range that is when
the Shims are too thick,this is a stupid practice and is usually done by
inexperienced or those wanting a few more Dollars for the same Job. Jaguar
seats are best left alone,many many heads fail after Seats fitted, in
practice the Jag head Flows more with the valves sunk further into the
Combustion Chambers ,so the Seats have a lifespan of about 100 years, with
the Inlets you cut the Seat & fit a Bigger 17/8 " Inlet Valve,this then
moves the Valve Head back into the Arena and the Shim Range is there for the
collect Clearance. You do not need new seats when fitting the larger inlet
Valve,that’s a Con Job.
Regards
Terry
@JAGPRO__________________________________________________
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