Jag-lovers XK Engine Tappet Retainer Stakedown FAQ

                  (V1.0 rough draft Dec 1996)





                      Lawrence Buja

                  southern@ncar.ucar.edu





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A. Overview: 

Jaguars with the classic XK straight-6 dual-overhead valve engines are
prone to having the steel tappet guides in the aluminum head come loose
and crash around inside the engine with disastrous results (see section

C).

A common fix is the "tappet guide stakedown kit" which mechanically 
holds the tappet guides in place.  

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B. Questions:

1.  WHICH JAGUARS ARE AFFECTED BY THIS PROBLEM?

    This problem does NOT affect the V12 engined Jaguars.  (all years)
    This problem does NOT affect the XJ40 and X300 sedans. (post-1987)

    This problem may occur in any of the Jaguars with the classic XK
    straight-6 2.4L, 3.4L, 3.8L and 4.2L displacement engines.

    Since these failures appear to be related to the degree of heat
    cycling which the engine experience, the most susceptible engines
    seem to be the exhaust sides of later, emissions equipped, 4.2L in
    XJ-6 sedans in the years 1974-1987.

2. HOW TO I KEEP THIS PROBLEM FROM DESTROYING MY ENGINE?

    The most common fix is to install a "tappet guide stakedown kit"
    which mechanically holds the tappet guides in place.

    The stakedown kit are three small metal plates bolted to the head
    underneath the camshaft on the exhaust side of the engine (see
    question 8).  These metal plates hold the press-fitted tappet guides
    in place.

3.  WHAT WILL HAPPEN IF I DON'T HAVE THESE RETAINERS INSTALLED.

    If you own a 4.2L XJ6, you stand a non-zero chance of destroying
    your engine.  Replacement XK engines cost around $US4000.
    See the first posting in section C.

4. HOW MUCH WILL IT COST TO INSTALL THE TAPPET GUIDE RETAINERS?

   The retainer kit is relatively inexpensive, around $30.
   Expect to be charged around $300 for a mechanic to install it.

5. I LOVE TO SAVE MONEY, CAN I INSTALL THEM MYSELF?

   This is probably not a do-it-yourself job unless you are very
   experienced with engine work (see the postings below).

6. IN SPITE OF THE FACT THAT I OWN A LUXURY JAGUAR, I'M REALLY
   CHEAP|POOR|FRUGAL.  HOW DO I DO THIS WITHOUT SPENDING ANY MONEY?

   Old graybeard XK mechanics have been known to use machine-screws
   screwed into the aluminum head to mechanically hold down the 
   tappet guides.   Do this at your own risk.

7. HOW DO I CHECK THAT MY JAGUAR HAS HAD THE TAPPET RETAINERS FITTED?

   The cheapest and easiest way is, with the engine off and cool,
   to take off the oil cap and feel under camshaft, between the
   first two tappet locations, for the metal retainers mentioned
   in question 8.

8. I'M STILL NOT SURE, HOW DO I TELL FOR SURE THAT THE TAPPET GUIDE 
   RETAINERS HAVE BEEN ADDED TO MY ENGINE?
   Viewed from the top, your engine looks like:

      ___       Intake side

     |   -------------------------.

     |                            |  Figure 1  (top view)

     |   -------------------------'

     |--| *   *    *   *    *    *

     |   -------------------------.

     |                            | 

     |___-------------------------'

                Exhaust side

	Take off the valve cover on the exhaust side of the engine.

    Disregard the round camshaft which sits on top.  Underneath
    the round camshaft, you will see the tops of the 6 exhaust
    side tappet guides staring up at you as shown in Figure 1.

      ___       Intake

     |   -------------------------.

     |                            |                      

     |   -------------------------'

     |--|   

     |## -------------------------.

     |##+ O   O    O   O    O   O |  Figure 1  (top view)

     |___-------------------------'

                Exhaust     

    

    Again, disregarding the round camshaft, the retainer kit in my
    XJ6 looks like:
   

     |--|

     |## -------------------------.

     |##+ O===O    O===O    O===O |  Figure 2a  (top view)

     |__--------------------------'

               Exhaust 

    where each === is a metal retainer.

    From the side, it looks like:


     |##+                         

     |##   ===      ===      ===  |  Figure 2b  (side view)

     |##  O   O    O   O    O   O |

     -----------------------------

               Exhaust
   

    The retainers themselves are metal plates which look like:


        ___________________          Figure 3a: Top view.

       /                   \   

      /    *          *     \                * indicates a bolt

     |                       |

      -----------------------

    

           *          *              Figure 3b: Side view

     =========================

      =======================

           *          *

           *          *

    

    Note: The retainers are not centered on the 9 or 3 o'clock
          positions, as shown in Figure 2.  Rather they are shifted
          outboard from center and grip the tappet guides at the 7 or 4
          o'clock position.

    Also, I'm assuming the existence of the lips shown in Fig 3b.  For 
          some reason, I think they're there, but I've never had the
          retainers off, so I haven't looked underneath them.
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C. Postings from Jag-lovers on the subject:

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-From: Randy Wilson 
-Subject: Re: XJ6 - SIII: tapping noise from engine
-Date: Wed, 18 Dec 1996 23:42:08 -0500 (EST)

>My 1985 XJ6 4.2 (88,000 mi.) developed a tapping noise recently.  My mechanic
>removed the valve cover and discovered a broken metal sleeve (valve lifter).
>Unfortunately, metal pieces are circulating throughout my engine.  I'm looking
>at an engine rebuild or a new engine.  My mechanic says he can install a new
>engine for around $7,500.  A mechanic who read my message posted in the
>CompuServe Auto Forum says that new engines are not available and that a rebuild
>should cost between $3,500 and $4,500.  

>I'm most disappointed. I was under the impression that the XK engine was one of
>the best. Has anyone else experienced this problem?  And, can anyone shed light
>on this new vs rebuild dilemna.  I'd appreciate advise.
>Mark B.

Common enough. You missed the critical beginings of the tapping, when the tappet
guide first started working it's way up (it broke the tappet guide, BTW, not
the lifter). This is exactly what the stakedown kit is for.

Rebuilt engines (including installation) typically run in the $4K range.

However, what evidence do you have that the entire engine is shot? Yes, the
tappet guide needs to be replaced. If the damage is not too severe, it is
possible to replace it and install the stakedown kit with the head still on
the car. However, I do not recommend such things. Pull the head, do a proper 
installation of the guide, and a valve job while you're in there.

If the engine has had some milage since the guide got broken, I would not be
too concerned about the metal pieces. The big chunks will migrate to the
bottom of the sump, and possibly out during the next oil change. the littlest
ones, the filings that can make it through the pickup strainer, will get
trapped by the oil filter. The biggest danger is the pieces getting caught
up in the timing chains/sprockets on their migration downward.

   Randy K. Wilson
   randy@taylor.infi.net
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-Date: Fri, 24 May 1996 14:01:06 +1200
-From: John McDonagh 
-Subject: Re: xj6 Stakedown Kits

I have heard of the problem with loose tappet guides but it is very
uncommon in New Zealand and no one here "stakes down" their guides as a
matter of course. This would tie in with the posting about emission
controls and higher engine temperatures. We have no emissions
requirements on vehicles and overheating problems in Jaguars are also
uncommon so I would assume all these things are interrelated.

John McDonagh
Department of Accounting Finance and Property Studies
Lincoln University
Christchurch
New Zealand

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-Date: Thu, 23 May 96 13:28:35 PDT
-From: spe00@eng.amdahl.com (Silas Elash)
-Subject: Re: xj6 Stakedown Kits

David,
I have heard all kinds of opinions on the list.  I talked with a
mechanic about it, and he told me that the problem really started to
appear on the XJ6 when emissions testing required a higher combustion
chamber temperature to get the emissions down.  So the later model cars
have a more restrictive water inlet into the head.  This higher temp
causes the problem due to the continual cycling from hot(now hotter) to
cold, etc, etc...- over time the cycling loosens the tappet sleeves.  He
told me that the problem was unusual on an older car like my 62 MK2,
unless it had been over heated.  The older motors run cooler and thus
have less stress on the tappet guides due to the lower temp range they
cycle thru.

All any of this tells you is that odds are lower on an older car.  If
the car has been run hot- maybe you get the problem.  Later model
"hotter" engine, more likely to get the problem.  I would think that a
very old engine could also eventually have the problem, just because it
has gone thru more cycles???

Anyway, thats the scoop as far as I can tell.  Predicting if your car
will have the problem, is like rolling dice.  I guess most of us don't
feel lucky- or don't want to risk it, so we stake them down.  I don't
know if I would do it just for the sake of doing it - if I had no other
reason to open things up.  In fact I have not done it on my 84 XJ6
(59,000mi.), but it has relatively low miles and I am going to wait.

Good luck,

Silas Elash
62MK2
84XJ6

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-Date: Mon, 16 Sep 1996 19:56:02 +0100
-From: Jeffrey Gram 
-Subject: XK engine stake down

XK engine stake down 

Hi, As some may remember I fumbled my way to mount a stakedown kit with
the head on.

It is not as easy as it sounds the hardest part being drilling exactly
where you want to drill. The drill bit is very prone to "wandering"
while getting the first grip in the light alloy, and the tolerance on
the holes in the stake down plate do not allow much error. I had to
drill up the holes on several, and I damn near splintered a tapped
guide, when "easing" one into position with a sledgehammer. One tappet
bucket didn't fit after the stake down kit was mounted, until i realised
the guide was under deformation..... Own fault of course. Off again and
drill the hole in the stake down plate bigger to correct for the drill
position error. One fatal error and the whole work is lost and
professional help is needed to get head off , new guides
in.... $$$$$$$$$$$$

Dont forget you need to get camshafts off, where there are other traps
laying waiting for the innocent DIY'er : you could lose a valve sprocket
bolt or lock plate down the chain housing - this will set the repair
back by another two weeks, getting either the engine front off (bonnet,
radiator etc.....or turn thecar upside down and shake it vigorously....

Or you could get the valve timing wrong an re-assembly - Just ask Ryan
Border :-)

Still want to do this  ?

OK :

Tapping in aluminium requires the tap to be wetted with alcohol, however
for this particular operation a more sticky material is better to get
the cut bits up. Compressed air is great (when all other oil holes are
covered up with cloth.

There is a way to tap which is called two step forward, one step back,
two step forward, etc.  This MUST be obeyed or the risk is a broken tap
in the head and then you are really stuck.

Holding the tap perpendicular to the head is also not that easy
especially if you have never done it before., buy extra taps and train
yourself on a scrap piece og aluminium.

Frankly speaking, I would not attempt this if I hadn't been drilling and
tapping for 25 years now on a DIY hobby basis, (Ok less experience will
also do). But realise there is a fair chance to get it wrong.

I will send you my description from February this year.

Regards Jeffrey Gram