Jaguar XJ-S. Manual - part 22

 
 

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Does anyone make Teflon valve stem seals for the XJ-S?  Carpentier: “Perfect Circle does, although unwittingly since I 
doubt they ever considered Jaguar engines as a possible application for their product.  Our valve guide diameter is 
0.502 to 0.501 in, that's essentially 1/2" or sixteen (16) thirty secondths of an inch.  Valve stem diameter is 0.3092 to 
0.3093 in, and that's within 3 thou of 5/16" or ten (10) thirty secondths of an inch.  These dimensions are a bit unusual 
but luckily match those of the first generation Chrysler Hemi engines.  Call Perfect Circle (they are a DANA 
subsidiary) and they will tell you:  "Yes, we manufacture such Teflon seals, part number D1610, available at any 
NAPA auto store". 

“There is a catch: if you go to NAPA and ask for this reference, they look it up in their computer and tell you it does not 
exist (never mind telling them what kind of car it is for...).  The last time I was in the US, I finally found a place in Los 
Angeles that would order them for me.  The seals actually came from a company called Silver Seals Products/Whip-L 
Products, Trenton, Michigan, 1-800-521-2936; their reference is DT1610 but the seals carry the Perfect Circle logo.”  
This author called that 800 number, and had a set of 24 Teflon valve seals on order in a matter of minutes and in hand 
in a week at a cost of less than a dollar each.  For those outside the US where an 800 number won’t work, their regular 
phone number is +1 (734) 479-2255. 

The OEM nitrile seals on the inlet valves are pressed over the valve guide until they snap into a groove around the 
guide just above the surface of the head.  The exhaust valve guides have no such groove.  This turns out to be a non-
issue with the Teflon seals; these seals press fit onto the OD of the valve guide, and therefore do not use the snap 
groove.  While the OEM seals are a simplistic piece of rubber, the Teflon seals include a metal ring on each diameter to 
provide a secure fit on the guide and on the valve stem itself. 

Besides the diameters of the guide and stem, there are a few other things to consider whenever fitting a non-OEM valve 
stem seal to an engine.  In this case, the OD of the base fits within the inner spring just fine.  The Teflon seal is a little 
taller than the original seal, which makes for a really close fit; the valve lift is 3/8”, and that’s pretty much right where 
the valve keepers sit down on the top of the seal’s lip.  If you intend to run an aftermarket cam with more lift, you’ll 
need to either use the shorter OEM seals or make some other changes, like shortening the keepers or the guides. 

Installation is not as simple as with the nitrile seals.  Carpentier:  “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.”  Note: on the valve stems, just below the groove, the part number is engraved; might as well 
leave the sleeve long enough to cover the number too, just to make sure you don’t damage the seals going over it. 

“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.”  
Clearly, you need to have the valve in place before installing the seal and you can’t remove it afterward, so make sure 
you are actually at the final assembly stage (all lapping completed, etc.) before installing seals. 

“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 chamfer, then tap it all the way in.  Don't hammer 
too hard though or the upper portion will shear off as you hit bottom.”  Note: this author has done this job, and it’s a lot 
easier than it sounds. 

 

EXHAUST FLOW LIMITATIONS:  Roger Bywater explains an inherent shortcoming of the H.E. engine:  “The small 
and pocketed exhaust valves are the real problem and is why all the high performance racing V12s have been based on 
the old "flat head" design.  Putting big exhaust valves in doesn't help because the chamber walls are so close and leave 
no room for flow around the edge of the bigger valve head.  In fact if the HE were not of abnormally high compression 
ratio, always a useful trick to get a bit more top end power out of an engine that doesn't breathe, it would struggle to 
produce the barely adequate power that it gives as standard.  You can build an HE to 6 or more litres (we used to do a 
6.3 using 98 mm bore and standard crank) but all you really get is more torque low down but not much more power.” 

 

 
 

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SODIUM-COOLED EXHAUST VALVES:  Roger Bywater continues about the H.E. head:  “As an economy measure 
the HE was outstandingly successful (helped by the 2.88 axle) but the severely shrouded position of the exhaust valve 
certainly hinders the pursuit of high power and increases the thermal loading the valve is subjected to.  To withstand the 
rigours of sustained high speeds on German autobahns sodium cooled exhaust valves were introduced on cars for the 
European market. 

“All but the early European H.E. V12s and also the H.E. headed 2.9 AJ6 engine had sodium filled exhaust valves under 
the same part number EAC 7318 for both engines.  They were introduced first on the V12 for Germany/Switzerland 
then later for UK, etc.  I am not aware of any corrosion problem but it would surely be a bigger problem at high 
temperatures rather than while standing. 

“The valve stem is roughly half filled with sodium which melts and acts as a "cocktail shaker" increasing the rate of 
heat transfer from the valve head to the stem.” 

 

HEAD GASKETS:  The OEM head gaskets are a metal-fiber-metal sandwich.  Payen makes such gaskets.  However, 
Clough (England) makes head gaskets for the Jaguar V12 that are the opposite: a fiber-metal-fiber sandwich.  One 
report:  “One was extremely difficult to get over the studs - I believe made wrong or shrunk some.  It ripped!” 

The Jaguar V12 rarely suffers head gasket trouble, which may mean pretty much any head gasket will do the job, but it 
also might mean that the OEM gaskets are really good.  Try something different at your own risk. 

Martin Walker says, “H.E. gaskets don't seem to fit the pre-H.E. heads.  I bought a complete H.E. gasket set from a Jag 
dealer and had to return it because the coolant passage openings in the head don't all line up properly.” 

Can you just cut suitable openings in the gasket?  Don Miles:  “Don't do it!  Don't do it!  I repeat again, don't do it! 

“What happens is, you allow the internal softer material to rot/crumble and to have a very large edge to escape.  Not a 
problem to start with if you are one of the crap screen users as it will be prevented from junking the rad. However, 
when the soft material crumbles at the 'fire ring' around the cylinder head the 'nip' is reduced and gasket failure follows. 
 On a race engine with 10:1 or more this can be in 2 weeks.  On a normal road V12 it will clearly be longer but this is 
pretty immaterial (pun intended) as the loose soft part would have long since junked your engine as it blocks both 
screens.  Without the screens it will cost you a new rad. 

“How do I know this?  Don't ask, but we astonished ourselves and changed the offending gasket in 35 mins and won 
the race.  The other gasket was done later at a more leisurely pace.” 

 

FIDDLING WITH THE TIMING CHAIN:  If, for some reason, your timing chain isn’t sitting on the sprocket on the 
holding bracket when you put the head on, David Johnson says, “if you have already installed cam, be sure that you 
take the moment and hook the cam chain over the bracket meant to hang sprocket on.  I looked at it and told myself, 
"Why bother?  I can simply reach down there and pull it up."  Ain't so.  The flange and bracket are just this much too 
close to squeeze the chain through.” 

 

CYLINDER HEAD NUTS/WASHERS:  The thick washers under the 7/16” nuts are quite suitable for the job, and the 
thin washers under the 3/8” nuts under the intake ports seem to work well enough.  The same thin washers used under 
the 3/8” nuts along the exhaust manifold edge of the head don’t cut the mustard, though.  They are likely to be “dished” 
where the nut has been pressing them down into the soft aluminum of the head.  The implication: as the washers distort 
and the local area of the head is dished, the tension on the stud is relaxed, reducing compression on the head gasket and 
increasing the chances of a head gasket failure. 

To improve this situation, one of three tactics is recommended:  Replace the washers with thicker washers; replace the 
nuts with washer-face nuts that will contact the original washer across most of its surface; or -- as a minimum fix -- 
install two washers under each nut.  CarQuest auto parts (and undoubtedly some other better auto parts shops, but 
notably not some of the discount or bargain auto parts stores) offers a Dorman “manifold stud washer” number 685-050 
which is quite suitable for this task.  Note that these washers are not found on a bubble card on a rack, but rather in a 

 
 

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case of heavy red and black metal drawers that form the Dorman display -- often found behind the counter.  Look in the 
drawer labelled “manifold studs”.  This washer is about 1/8” thick (like the washers under the 7/16” nuts), fits very 
snugly around the 3/8” stud, and has a somewhat larger OD than the flimsy original washer. 

With these washers under the original nuts, you can actually feel the difference as you’re torquing them up.  It feels 
much more solid, attaining the specified torque promptly and securely, rather than feeling mushy. 

 

TORQUING THE CYLINDER HEAD NUTS:  The nuts holding the heads to the block, as in other engines, require 
careful torquing in progression to ensure proper sealing of the head gasket.  However, there are two groups of head nuts 
on the Jaguar V12 that cannot be tightened with a socket on the end of an extension, meaning they are difficult to use a 
torque wrench on.  One such group of nuts is the row of 9/16” nuts on 3/8” studs along the top edge of each head, 
within the vee; these are underneath the intake ports.  The other group is the row of 11/16” domed nuts on 7/16” studs 
just under the tappet block on each side; these would be a snap if you were torquing the head nuts without the tappet 
block on there, but with the tappet block in place you can’t get the socket over the nut. 

This job calls for a tool called a crowfoot (or crow’s foot) wrench.  This tool looks like just the business end portion of 
a wrench with a square drive hole for attachment of a ratchet and extension.  Since they are useful tools anyway and 
come in handy in other hard-to-reach places, it is recommended an entire SAE or Imperial set be purchased.  If you 
wish to buy only the crowfoot wrenches you need for this job, Sears sells crowfoot wrenches individually.  The nut and 
stud sizes mentioned above were apparently maintained throughout the life of the Jaguar V12, even when many of the 
other fasteners on the engine switched to metric. 

There are actually at least three different types of crowfoot wrenches, so you might want to consider your choices 
before buying.  The most common type looks like the business end portion of an open end wrench, so it can be slid onto 
the nut from the side.  It operates on only two corners of the nut.  The head area must be made fairly broad (like any 
open-end wrench) in order to give it adequate strength to prevent it from spreading and rounding off the nut under 
torque.  Sears Craftsman crowfoot wrenches are this type. 

David Johnson suggests that, if you can find a set, buy box end crowfoot wrenches, since the torque applied to the 3/8” 
head nuts threatens to spread the 9/16” open end crowfoot and round the corners of the nut.  “Mine are from Snap On.” 
 He’s right about the threat; this author used an open end set successfully, but there was clearly very little strength to 
spare.  Box end crowfoot wrenches (like other box end wrenches) cannot go on a nut from the side, they must come 
down on top. 

The third type crowfoot available is halfway between the open end and box end; they look like the business end of a 
“flare nut wrench”.  In other words, they look like the end of a box end wrench that someone has cut a slot through at 
the end.  It looks like the crow was pigeon-toed; maybe they should be called pigeonfoot wrenches!  They cannot go on 
a nut from the side, but they can go onto a bolt (or metal brake line) from the side and then come down on the nut from 
above.  Most such wrenches are “six point”, meaning they have five points -- the slot takes away one of the six points, 
so this type wrench operates on five corners of the nut. 

There is another functional difference between the open-end style crowfoot and the flare nut style.  The open end style 
is symmetrical when looked down on from above; if you flipped it over, it wouldn’t make any difference (except for a 
raised area where the square drive attaches).  So, you will need to have enough room to turn the nut 60° at a time, slide 
the wrench off and move it back to the next flat and go again.  But the flare nut style, despite being a six-point style, 
offers another option.  The square drive attachment is 30° off one flat of the hex, so if you can’t turn the nut the full 
60°, you can take the crowfoot off the end of the square drive extension, flip it over, and turn the nut the next 30°.  That 
would make for a long, slow job of tightening a nut, but it’d be better than being unable to tighten it at all. 

Finally, one more functional difference worth noting.  The open end type of crowfoot wrench, like an open end wrench, 
can be used while held tilted a bit upward or downward from square on the nut.  Since they only contact on two 
opposite flats, they can withstand a considerable amount of misalignment during use.  With a crowfoot, this means that 
you don’t need to be holding the ratchet extension perfectly parallel to the centerline of the bolt or nut, but you can tilt it 
away from that centerline or towards it a little bit.  The box end or flare nut types of crowfoot, on the other hand, fit 
very securely on a hex.  If misaligned, you won’t even get it on.  This can be a blessing or a curse depending on what 

 
 

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you’re doing, but mark my words, whichever type you get you will eventually find a situation where you wish you had 
the other. 

Although listed third here, the flare nut style crowfoot wrenches are perhaps easier to find than the box end style.  John 
Robison says, “Here is the link for the set I bought... 

 

 

http://tools-plus.com/hand-tools-wrenches--crows-foot-.html

 

J. C. Whitney (page 691) offers both open end and flare nut style crowfoot wrenches in SAE or metric sets -- for about 
$10 a set!  Really high quality stuff, obviously. 

When using crowfoot wrenches in conjunction with a torque wrench, the crowfoot should always be attached to form a 
90° angle with the handle of the torque wrench.  The effective lever length of the torque wrench (distance from the 
handle to the centerline of the bolt or nut being torqued) is not changed.  If the crowfoot is attached in line with the 
handle, the lever length is altered, and the torque readings will be inaccurate. 

For some reason, some people have arrived at the conclusion that extensions make a difference in torque wrench 
readings.  They do not; use whatever extensions you need to to get the job done.  Swivel joints can make a difference in 
torque readings; if you absolutely have to use a swivel joint with a torque wrench, at least attempt to hold it as straight 
as possible. 

With the 11/16” domed nuts under the tappet block, the box end and the flare nut type crowfoot wrench may cause 
trouble.  The problem at this spot is that the domed nut is tall and comes up pretty close to the surface of the tappet 
block.  Since these two types of wrench have to go over the nut to get on, they must be thin enough to fit between the 
nut and the tappet block at that point.  Craig Sawyers bought an expensive flare nut type -- actually a 12-point flare nut 
type -- that didn’t work.  By lining up the gap at the end, he could get it on, but as soon as he turned the nut he 
effectively trapped the tool; it wouldn’t come off.  “If you get one flat of turn on it, it won't come off the nut.  If you 
back it off slightly so that it clears the nut, you can't get it back on for the next turn.  Britool AFC687...  This beast is 
0.525" thick, and the diameter of the surround to the socket part is 1.275".  The open end is 0.57" wide and parallel.  
And it is 12-point and was not cheap - I bought this sucker to do up those 11/16" nuts under the tappet block, and was 
not pleased when it didn't work out.” 

Sawyers found an alternative to the crowfoot wrench for the 11/16” domed nuts:  “I ended up getting a friend with a 
lathe to turn a shoulder on a standard socket so that it would snug under the tappet block.  Worked a treat.”  Of course, 
cutting on that fancy crowfoot probably would have worked, too, but the socket was cheaper -- and since it worked, the 
socket was arguably preferable to the crowfoot for this job.  In fact, if you plan to retorque these nuts later, you’ll find 
this modified socket vastly preferable.  Basically, Sawyers machined the square drive end of the socket down to about 
as small as he could get it, leaving the large diameter portion as short as possible.  “The part around the socket, 0.935" 
diameter (ie, as supplied) and 0.7" to the turned shoulder.  The turned down part (where the 3/8" drive fits) is 0.67" 
diameter and 0.49" long from the shoulder to the top.”  Note that the 0.7” dimension is what’s critical, and the 
maximum that will work may actually vary a bit from car to car.  If you start with a socket that is too tall, you won’t be 
able to cut the shoulder that far down without cutting the socket in half -- but you can shorten it up by simply grinding 
off the end of the socket until it goes on. 

There are also problems using a crowfoot on the 9/16” nuts.  These nuts sit in a ledge cut into the head, but Jaguar 
didn’t cut the ledge any deeper than they had to.  There’s very little clearance between the points of the nut itself and 
the machined surface behind it.  This is part of the reason the open end crowfoot threatens to spread; if you put the 
crowfoot all the way onto the nut, you can’t turn it very far before the wrench runs hard against that machined surface, 
so instead you pull the crowfoot back a little and tighten the nut with the tips of the crowfoot.  Using a box end, as 
Johnson recommends, will mean it needs to wrap all the way around that nut and therefore must be pretty thin-walled -- 
but box ends are generally pretty thin-walled, especially from companies like Snap-On.  The flare nut style may have 
more troubles, since the claws of the crowfoot have to be beefier to make up for the loss of strength that comes from 
opening a gap at the end, and so may have trouble turning without jamming against the machined surface.  It may be 
possible to use either box end or flare nut style crowfoot wrenches by fitting them to the upper half of the nut only, 
staying above the surrounding metal of the head; since they’re grabbing 5 or 6 points they should still be able to apply 
adequate torque.  Results may vary from casting to casting.