Jaguar XJ-S. Manual - part 20

 
 

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mount on one side, putting a jack under the front of the engine and jacking, causing the engine to rise and tilt.  After 
one head came off, the engine was lowered, the mount reconnected, the other mount unbolted, and the engine jacked 
back up so it tilted the other way to remove the other head. 

David Johnson says, “It was easier for me to remove both motor mounts and lower the engine to get enough clearance.” 
 Johnson goes on to say that, even though he pulled the heads with the manifolds still attached, he went the other way 
on reassembly.  “I did that because I couldn't get 2 nuts off the bottom because some &^%%$ had galled up the threads 
and the nut wouldn't come off, and the stud was trapped.  Now that I replaced the studs with new, and with the ever-
present anti-seize it was much easier to put it on after.” 

Whatever method is used to deal with the exhaust manifolds, make sure to take enough notes to be able to reinstall the 
heads and reassemble the car. 

Tip:  If the tappet block is off, you may find it helpful to unscrew and remove the rear pair of cam bearing cap studs to 
ease clearing things while getting the head in and out of the engine compartment. 

 

STUCK HEADS:  When you actually get to pulling the head off, if it’s never been off before you’ll probably find it 
stuck.  In general, being stuck means one of two things:  The head and block are glued together at the gasket, or the 
studs are stuck in the holes.  The difference becomes evident when you actually get it loose:  If it was stuck at the 
gasket, then once it’s broken loose it slides easily off the rest of the way off the studs.  This is typically not the case with 
the V12 heads, which have metal-faced gaskets that don’t stick much, but the crud really builds up around the studs 
(several of which are immersed in coolant) and makes it difficult to get the head off every bit of the way.  You might 
get it an inch up and still be having difficulty moving it. 

This author will express an opinion here:  The stuff plugging the openings around the studs is very likely the Barrs 
Leaks that Jaguar recommends putting in the coolant.  Heads that have been off before and never exposed to Barrs 
Leaks again typically come right off without any more effort than lifting by hand.  Of course, rust particles or other 
deposits in the coolant might also contribute to the jamming, but careful maintenance of the coolant seems to avoid 
those problems. 

Loren Lingren sends this tip:  “With all the nuts removed, try to wiggle the end of each stud by hand.  The stuck ones 
will not move.  Begin soaking each stud with a good penetrating oil.  Get several 7/16 SAE nuts (Don’t use the head 
nuts unless you have extras) and an air hammer with a tie rod tool attachment.  The idea is to vibrate the studs with the 
air hammer, protecting the threads with the disposable nuts.  Caution must be used not to bend the studs or gouge the 
head surface.  Continue to apply penetrant as work is done.  As the studs loosen, the penetrant will disappear down 
between the head and stud.  I have used this procedure successfully for several years in removing even the most 
stubborn heads, 6 or 12 cyl, without any expensive side effects.” 

Other substances suggested for loosening the crud in the stud holes include oven cleaner, alloy wheel cleaner, 
phosphoric acid, Nitromors, lemon juice, and Coca-Cola.  Dr. Karsten Eller, chemist, says to forget about the oven 
cleaner:  “Oven cleaner is mainly caustic soda, i. e. NaOH.  The sodium hydroxide attacks the protective alumina 
coating on the aluminium and also dissolves aluminium metal: 

 

2 Al + 2 NaOH + 6 H2O = 2 Na[Al(OH)4] + 3 H2 

“Use of oven cleaner is therefore strongly dissuaded from.” 

Eller says acid will be fine, however.  Mike Morrin says, “Someone suggested using phosphoric acid (rust killer) as it 
dissolves the rust without damaging the aluminium.  He also suggested moulding little dams in plasticine to hold the 
stuff around the studs.” 

Regarding the use of Coke, Craig Sawyers says, “Now here's an interesting connection.  Coke contains phosphoric acid 
(that is why it rots your teeth).”  The stuff worked just great for James Dichter:  “You know it's amazing what a little 
Coke will do.  I'm beginning to wonder if we should be drinking this stuff.  I'm also contemplating marketing it under a 
different name for the purposes of unsiezing head bolts...” 

 
 

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John Warr says, “Nitromors is not actually acidic - It contains dichloromethane, which will remove most hydrocarbon 
based gunge.  It plays havoc with the skin however, and the vapour will go across most types of glove. 

“I think alloy wheel cleaner will do the trick quite well.” 

Of course, another fine idea would be to unscrew the studs and take them out.  Probably not even worth trying, though; 
you can’t get very good access to the studs with the head in place, and they are likely to be trouble to remove -- see the 
section on replacing head studs on page 80. 

The April 1987 issue of Skinned Knuckles magazine included an article on removing aluminum cylinder heads by Earl 
Reynolds.  The primary suggestion is citric acid, with an editor’s note mentioning phosphoric acid and Coca-Cola as 
well.  But the article provides yet another idea: using an electric arc welder to heat the studs.  “Attach the rod holder to 
the top of the stud and the ground clamp to any other part of the engine block.  Run the machine for a minute or two 
and the stud will become extremely hot and expand in diameter, crushing the fuzzy corrosion products in the process.  
When the stud cools and contracts, a void space is produced between the stud and the cylinder head.  One minute with 
the heat on and five minutes of cooling the cable down will do the trick.”  Note that, since there’s probably no good 
way of knowing just how hot the welder got the stud, it’d probably be a good idea to replace all the studs that were 
heated in this way just in case they lost strength in the heating.  With any luck, the heating also made it easier to 
unscrew them.  It is suggested that you review the prices of these studs before you choose to attempt this method. 

If persuasion fails, use force.  Malcolm Scott suggests, “I bolted on to the exhaust studs a heavy metal plate that had 
sufficient rise in it so that I could use a hammer.  This separated the head from the block and loosened the head from all 
studs along the exhaust side.  However, two studs near the rear under the inlets were clearly holding things up.  On the 
HE heads, the inlet tract protrudes over the smaller studs.  I put the nuts back on the two offending studs and put solid 
packing between the nut and the bottom of the inlet.  I then carefully wound the nuts off and the heads pushed off 
easily.  Because the studs had grown into the head, they would not let go until the head was about 0.5 inch off.  This 
required loosening of the nuts and adding solid packing (I used other nuts and washers).” 

Richard Chapman suggests that you remove the cam so that all the valves are closed, then feed rope into the spark plug 
holes on cylinders 1 and 6.  Turn the crank over and let the pistons push the head off.  Might also work on cylinders 2 
and 5. 

John Napoli:  “There is a technique that we used successfully on much lesser cars.  The trick is that you need to try this 
before you dissasemble very much.  The trick is to loosen as many head nuts as you can access, and then run the 
engine!!  One good stab of the throttle is usually all it takes.  The head quickly 'pops' a bit. Shut it down and then 
remove the heads normally.  You only need to loosen the nuts a couple of turns, and it often doesn't matter if you can't 
get to 'em all.  We used to do this on engines where, for whatever reason, we anticipated problems in getting the heads 
off.” 

If nothing else works, John Goodman describes a homemade tool that will get the heads off:  “1/2” steel plate slightly 
wider and longer than the cyl head.  Drill two rows of holes down the centre to line up with the camshaft bearing cap 
mounting holes, bolt plate onto camshaft carrier using the existing bearing cap studs.  Screw long bolts through 
threaded holes in the outside edges of this plate which line up with the cyl head retaining studs, the ends of these long 
bolts had “cups” to locate them over the cyl head studs.  Next just torque down evenly with a few smacks from a BRO 
hammer and the heads come off.”  If you have the tappet block off, you might be able to use it as a template to mark 
where to drill holes in the plate. 

Alternatively, a smaller, more compact set of tools that work essentially the same way as Goodman’s massive plate can 
be fabbed up quite easily.  First, purchase a length of steel bar 1/2” thick and 1” or 1-1/2” wide and cut two pieces 4-
1/2” long from it.  Drill two holes and drill and tap two other holes in each piece as shown in Figure 6.  Into those 
tapped holes, thread 3/8”-16 bolts that are at least 5 inches long and threaded all the way to the head. 

 
 

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tap 3/ 8"- 16

 

11/ 32" dia

 

1"

 

1 1/ 2"

 

1"

 

1/ 8"

 

 

Figure 6 - Head Jacking Tool 

If you want, you can use 3/8” fine thread bolts and tap the plate accordingly, or even 8mm metric stuff -- whatever 
is easiest to find in your area.  You can use threaded rod, but you’ll need to find a way to turn the threaded rod -- 
weld a nut onto it, bend it 90º at one end, whatever.  If you don’t have a tap or don’t want to bother, you can just 
drill 3/8” holes and put nuts on the back side of the plate, but it’ll make the tool a little clumsier to use. 

The tappet block should be in place, and you’ll need to remove the bearing caps and the camshaft.  If you’ve already 
removed the tappet block, just slide it back on; without the tappet block, it’s too easy to bend the studs using this tool.  
There are seven pairs of studs for cam bearing caps on each bank; this tool can be used on the 2nd, 3rd, 5th, or 6th pair. 
 Fit these two plates to the 2nd and 6th pairs and put nuts on to hold them in place.  You might need to put some spacers 
under the nuts on the studs -- 3/8” nuts work fine. 

To begin with, install some generic nuts on the top of each of the four head studs that will be involved, threading them 
on only a couple turns.  When the jacking screws are inserted into the center of these nuts, the nuts will keep the screws 
from walking off the end of the stud.  However, when the head has been lifted to the point where these nuts keep it 
from coming any further off, you’ll have to stop everything and remove the nuts.  Things may be moving well enough 
by that point to continue without anything to hold the jacking screws centered, but if not a few small pieces of  7/16” ID 
tubing slid over the studs will help -- or maybe some 1/2” nuts.  Once the jacking screws enter the holes in the head, 
there is no further need for such things, the head itself will hold the jacking screws aligned. 

It may be possible to get a mildly stuck head loose with only one tool by fitting it to the 2nd pair of studs, getting that 
end loose, then relocating it to the 6th pair and getting that end loose.  But since the trouble is likely to be from junk 
packed around the studs and will be trouble all the way up, it’ll be a lot easier to make two of these tools and jack both 
ends simultaneously. 

When jacking, take care not to allow the head to tilt inward or outward; tighten both jacking screws on each tool 
evenly.  If the head cocks, it just jams worse on the studs. 

Note that the weak point on these contraptions is probably the cam bearing studs themselves.  Don’t go cranking real 
hard; if the head just won’t come loose, find a way to apply more lift elsewhere -- don’t just pull the studs out of the top 
of the head.  Since they’re only attached to two studs each, these little tools won’t apply the lifting force that 
Goodman’s massive plate will, but it should get most heads off.  If more force is required, two more plates could be 
fabbed and installed on the 3rd and 5th pairs of studs to apply more oomph.  You could even fab a fifth plate with no 
1/8” offset between the pairs of holes to use on the 4th (center) set of studs. 

 
 

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Matthias Fouquet-Lapar quotes the "XJ-S issue" (Volume 8 Number 3 January/February 1996) of Jaguar World, page 
57 : 

"Cylinder heads can be a nightmare to lift due to the inter-action of steel studs and alloy heads.  However, 
Classic Spares do market a tool of their own design that makes light work of the job.  Be warned, you will need 
it." 

See page 690 for Classic Spares.  There are also reports that John’s Cars (page 715) offers such a tool. 

 

ONE HEAD OR BOTH?  If a valve seat drops in one bank, some people want to know if they can just pull the head 
from that bank and leave the other one alone.  If the seat only drops a bit but stays in place, you might get away with it. 
 If the seat actually falls out and breaks up, apparently not.  Greg Wells of Concours West says, “If one or more seats 
has dropped and shattered, you must pull both heads, as the pieces will always have been tossed into the other head by 
the strong intake plenum reversions.” 

Aw, c’mon, that’s gotta be BS!  The two intake manifolds are completely separate, connected only by a 1” balance 
pipe.  Parts of a valve seat would have to go through that balance pipe to get to the other side!  “That's the only 
explanation I can offer.  This is not based on supposition but is something I have witnessed several times.  The seat 
pieces in the other bank (opposite the dropped seat) are pretty small and since the balance pipe is the only connection, I 
have to assume this is the case. 

“The last one I recall had dropped a single seat on the LH bank. Two of the LH pistons had shard embedded in them; 
four of the RH pistons also did.  The only seat missing was on the LH side and the broken seat pieces were small, on 
the order of 1/8" or so.” 

More testimony from Chad Bolles:  “Yes, it is possible for broken pieces of valves and seats to end up on the other side 
of the engine.  Been there done that.” 

And Roger Bywater:  “What seems to cause it is that if the exhaust valve is unable to seat and if there is a vacuum in 
the inlet manifold then exhaust gas will get drawn back out of the exhaust manifold and backflow through the inlet 
valve when it opens.  At moderately high engine speeds at light throttle this backflow could be quite considerable and 
might easily pull debris with it up into the manifold.  The good cylinder bank will be pulling better vacuum so there will 
be flow across the balance pipe and if circumstances are right then bits will end up making the journey across. 

“What seems at first to be impossible is actually not at all unlikely if the car continues to be driven in the damaged 
state.” 

 

SO YOU HAVE THE HEAD OFF:  Be sure and clean up the spark plug threads while you have the head off.  One 
excellent method is to get a suitable wire brush shaped like a “bottle brush” and screw the brush through the hole.  
Places that sell shotgun cleaning tools have an excellent selection of suitable brushes.  When clean, the spark plugs 
should spin all the way down by hand.  You might also want to address any spark plug threads that may be damaged; 
it’s easier to install an insert now than later on when the engine is together. 

If you have the A bank head off, it is suggested you go through the procedure of setting the location of the timing mark 
plate described in the section on ignition timing starting on page 125. 

If the block hasn’t been turned upside down in the midst of this job (!), there will be little puddles of coolant 
surrounding the liners.  Make sure you get this coolant out, and then scrape the bottom of these pockets with something 
pointy.  You’ll probably find a lot of junk, perhaps looking like sand.  It might actually be sand left over from the 
casting process.  David Johnson says, “I discovered that there was no coolant flow around the last cylinder on my A 
side!  The last liner is so close to the jacket that yuck had built up to the point that coolant would have had a hell of a 
time trying to flow around it.  I'd bet only about 1/2 the liner had coolant touching it!”  Whatever you find, get it outta 
there.  Small accumulations probably don’t hurt anything being there, but these pockets may serve a useful purpose in 
catching new crud floating around in the cooling circuit, and maybe once they’re full stuff starts plugging the radiator 
or something.