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3.1 - Sports Coils ( Dave Moore,  June 7, 2005 )

Do not expect the temperature gauge to sit still in the middle
like a modern car, it never will. The correct thermostat is 74C,
it is is normal for the running temperature to vary between 74C
and 95C. The engine is not overheating until the coolant boils.
The 3.8S suffers from a marginal cooling system, an undersized
radiator, a packed engine compartment and a small grill. Jaguar
spent a lot of time improving the cooling system in the saloons
because of overheating complaints, but the effective mods didn't
really arrive until the 420. The water pump impellor was redesigned
several times, the intake pipe enlarged, a cross flow radiator fitted
and the speed of the pump at idle increased several times.

It is not "overheating" until the coolant boils. If your system holds
pressure and you use a reasonable coolant mix, it should not boil over until at
least 110C. If your engine is in good condition, 90C or even 100C for a short
time will do no harm. Modern engines of the same construction operate at 120 C
with no engine damage. If you take a look in the archives you will find many
saloon owners whose internal thermostat turns red after 70C because of the
location of the gauge needle. This is a problem with the owner, not the car.

If you think you are having a problem and find yourself staring at the gauge,
first check the accuracy of the gauge, an IR thermometer is one way. The
comments about the thermostat are correct, it doesn't even start opening until
74C and isn't fully open until 85-90C. On a cool day you should be able to see
the thermostat open on the gauge as the temperature momentarily falls back, if
everything is working properly. To properly diagnose the cooling system you
need to first check that the system holds pressure. Then drive the car at a
reasonable speed for at least 10 miles on a hot day. The temperature should
stabilize somewhere between 74C and 90C. It may exceed 90C while sitting still
but it should drop down once you get air flowing through the radiator. If you
find that the temperature slowly climbs above 90C and keeps climbing and
never stabilizes, there is a problem.

The first thing I would do is to check the accuracy of the coolant
and the oil pressure gauges. They are both notoriously inaccurate.
I would remove the oil filter head and clean out the pressure
relief valve, check the seat and spring and fill up with 20/50W
oil. Then I would pressure test the cooling system. The 3.8S was
fitted with both a 4 psi and a 7 psi cap during production, the
limit is the water pump seal, not the radiator. Your radiator could
probably take more, but I wouldn't go above 7 psi. If the system
holds pressure, I would use a 7 psi cap and fit a 1 quart overflow
tank, it gives you a little extra coolant capacity and lets you
identify any internal leaks. A 70/30 water coolant mix with a
bottle of Water Wetter is a better idea than 50/50. The 3.8S uses
a by pass thermostat designed to allow coolant to circulate during
warm up while the thermostat is closed. It is designed to close
the by pass when the thermostat opens, but the manifold is often
corroded to the point where too much coolant by passes the radiator
when hot. If you don't have the correct themostat, try one, but
the solution is to fit a plug with a small hole in the by pass hose
to limit the flow. The factory recommended a 3/16'' hole, I use a
1/4'' brass NPT fitting.
There is no magic bullet for the 3.8 cooling system. The usual fix
for rising temperature at idle in hot weather is to fit an electric
pusher fan in front of the radiator. There are many options, I use
a 14'' Permacool that comes on at 95C and off at 90C. It only comes
on after prolonged idle in summer, but it stabilizes the
temperature. You can also replace the heavy stamped metal fan with
a modern nylon fan that moves more air at idle. Another good idea
is to add some ventilation to the engine compartment, the most
effective short of hood louvers is to vent the triangles in the
wheel wells in the rear lower engine compartment. The ideal set up
is to follow the factory's lead and fit a 4.2 pump with the larger
intake pipe and change the pulleys to increase the pump speed at
idle, but you also need to change the timing cover.

3.10 - Engine Removal ( )

It seems that the workshop manuals suggest engine removal is the first step in every process from replacing the clutch to fixing a scratch in the paintwork. Sadly the manuals are usually correct. There are two ways to remove the engine, out through the top, or down through the bottom. I recommend the second, both for reasons of safety (lots of mass swinging from a chain), and a decreased likelihood of destroying your paint with a rogue tail shaft (been there, done that, fortunately it was a parts car).
Disconnect the ancillary equipment (don't forget the heater hoses, grounding straps, speedo cables and other transmission-related wires), drain and remove the radiator. Remove the front suspension as described above, connect an engine hoist to the lifting strap (or fabricate one from a stout piece of steel angle stock), and take up some load on the hoist. Place a floor jack at the tail shaft of the transmission, and disconnect the engine and transmission mounts (including the stabilizer link at the back of the block), and the drive (propeller) shaft. Lower the engine-transmission combination down onto a conveniently located sheet of cardboard. With a friend pulling on the cardboard, gently lay the engine on its side. Disconnect the hoist and pull the engine out from under the car.

3.10.1 - Timing Cover Removal with the Engine In ( Saltwick/Eck,  November 23, 2004 )

Paul Saltwick wrote on Nov.23, 2004

If you look at the manual you will find ''remove engine'' in the
first paragraph of almost every chapter. Jagaur was clearly in the
business of selling cars, not making things easy for us.

You can remove the timing cover with the sump (and head) in place,
it is just a tricky job, and not the proper procedure, especially
if your goal is stopping leaks. The damper must come of, you can
use an impact wrench to remove the bolt, but not to replace it.
The bolt is torqued to over 100 ft lbs and can put up a good
fight. You usually need a puller for the damper because of the
split cone arrangement, you can make on using the pulley bolts and
a piece of steel. The front seal is shrouded and cannot be removed
without removing the cover or the sump first. To remove the cover
without removing the sump, you need to pull off the inner seal
track, a large bushing on the crankshaft that makes the seal
surface. This requires every tool in the box and some unusual
sounding swear words. With the seal track out, there is just
enough room to pull up the seal to clear the sump.

Unfortunately, for whatever reason, you have chosen a particularly
difficult task. If your goal is to seal up a leak, pull the sump
and do it the right way, or you will be disappointed. I would
never remove the timing cover without replacing the timing chains
and front seal and seal track, you don't want to be doing this
again anytime soon. You may want to read up on the front seal
choices and the oil slinger dilemma before choosing.

Mike Eck writes on Nov 23,2004:

The bottom line is, you can't remove the timing cover without dropping the
pan. Not only are those studs sticking down through the pan but the front
crankshaft seal is set in a groove in both the timing cover and the pan. To
clear the seal the pan needs to be dropped at least an inch, and you can't
do that with the front suspension in place. You'll also need to remove the
damper for the same reason.

With the radiator out, removing the damper is almost trivial. Remove the
keeper and unscrew the big bolt a couple of turns. Wedge a couple of
screwdrivers between the damper and the edge of the pan and give the bolt a
sharp whack with a large (3 lb.) hammer. The damper should pop loose, but
be restrained by the bolt.

Dropping the suspension isn't such a big deal either. I could have mine
completely off in 15 minutes, but you could probably get away with just
removing the 4 bolts that hold the front mounts and jacking the body up
until the front of the suspension drops an inch or so.

If you are capable of removing the head you should be easily capable of
handling this.

3.11 - Champion Spark Plugs for the MK2 ( jaguarjoe,  May 18, 2005 )

Jacques asked:

I've been told that the original Champion N8 spark plugs
listed for all 3.8 MK2's (no matter what the compression
ratio) were ultimately replaced by Champion N5C plugs.

Can anyone confirm this, or suggest a better plug for a 9:1 3.8?

pajtas response:

Hi, actually its been N11YC and N11YCC for the last 20 years or so,
but if you do a lot of city driving its N12YC. that being a bit

3.12 - XK Engine Build Information ( Terry Handley,  April 16, 2002 )

Really fitting HD8's to a B type head is not going to do anything to enhance
performance unless a host of other things are to be done, modifications need
to be compatible, go hand in hand to get any benefit, also more power costs
more $ per mile. An easy and economical upgrade for a Mk9 is to fit a 4.2
engine & Type 12 auto from an XJ6, these engines when rebuilt offer much
more grunt & they cost so much less to o/haul then a 3.8, the 4.2 fitted
with B Type head + 2 x HD6's go fine and are extremely torquey, the extra
torque allows a taller diff to be used with no compromise in acceleration or
economy plus the car with taller diff is much quieter than a std. 3.8 MK9.

Good B Type heads are becoming hard to find, look at the forgotten 2.4
engines as a source,it need to be taken out a little in the ports but
generally they are in better cond then B type heads from 3.4,3.8, engines,
sO many S/Port heads around & cheap.

It's 3 x HD6's or similar 13/4" SU's that will suffice for 350 +hp.

2 x HD6's will suffice on either a modified B type or S/Port head different
camshafts, better exhaust, modified inlet manifold, etc. enough flow for
maximum of about 260 real HP.

Only in the high rev range will there be any performance gain from fitting 2
x HD8's in place of HD6's and then it's marginal and not really measurable
by a stop watch, I suppose the larger 2" SU's look more tough, give more
muscle look.

I can't recommend any upgrade needles for HD6's with pancake air cleaners
firstly the filters differ in flow/resistance from make to make & also the
size of the Pancake Filters .

Really the MK9 filter works fine, however I realise why you wish to fit more
Sporty looking Filters.

I do have some old notes on needles that worked for me with std. XK
engine, pancake filters, B /type head etc, memory tells me they were what
suggested for the paper element or the XK ,3.4, 3.8 with the std. pancake
filters I will dig around on Monday for you, there would be some listers
that can suggest what has worked for them, I see SM needles have been

The adv. curve needs to be changed for pancake filters, see suggestions from
Jaguar/Lucas distributors, there is dist. specs in the older W/Shop manuals.
Treat the recommendations for Adv. Curves as a starting point only as new un
leaded fuels require some additional fiddling to get it all right, good idea
to use the highest octane fuel you can find, the higher octane un leaded
gives better economy so the few cents more at purchase is rewarded with
more MPG and usually better starting, smoother idle and more power.

Many people are finding after stripping engines that have been run for a
time on un leaded that their has been Detonation happening . scuffing of
piston skirts is often caused by detonation, broken rings, mouse eaten
piston crowns, worse holes in pistons. Detonation is a silent killer and
it's happening more often since un leaded introduction.

What's been required of late is to give more piston to cylinder clearance
and up the running temp of engines this necessitates also a higher poundage
radiator or header tank cap, the radiator needs to be able to cope with
extra poundage cap all new alloy radiators will cope.

Un leaded works better with engines that run at higher temp. then as for
std. XK engines, this sounds counter productive but in real time & for road
it works.

Early XK engines had differently made Alloy pistons and the alloy was of a
different mix, modern high silicon content low expansion pistons are fine
for most engines but with the XK engine despite newer composition pistons
being of a low expansion alloy etc. the pistons need more clearance this is
partly because the cam grinding of the pistons made to day is different.

Without going into the different pistons makes and designs of pistons used
in all the XK engines in real time they all mostly needed different
clearances then suggested in Jag W/Shop manuals, there was technical service
bulletins and news letters, telex's getting about many years ago with some
alarming at time advise as to piston clearances for some XK engines.

The biggest most common stuff up was & still is, people fit 3.8 Powermax
Pistons with 9-1 Compression in place of the std. 8-1 Compression piston
made by Brico, the results are not so nice with the skirts being damaged by
too tight a fit, not enough clearance.

Example of the mishaps happening now ,4.2 pistons are often given too little
clearance for the conditions the engine is to endure, also the engine blocks
are rusted in places that can not be attended to unless the cylinder sleeves
are removed, the said rust causes hot spots and too little clearance makes
matters worse, there is often then partial seizing and the engine is spoilt.
( no amount of hot tubbing will remove the said rust)

W/shop manuals and reco engine shop books have piston clearance for 4.2
engines as .0015",many give .002" ideal/preferred by me is .003".

Std XK engines from factory could have graded pistons & bore sizes varying
from std. to F to K =.005" to +.010" so each bore in an XK engine needs to
be measured and after hone a suitable piston used, problem is that only std.
sizes are now available, that is std. to .030" some .040" for 4.2, but then
with the latter one has a severe H/gasket overhang problem, all overhang is
severe but with the larger bore sizes the problem gets worse.(copper
h/gakets finished by hand is a good move)

3.8 engines are to be looked at very carefully, the new pistons around are
often 30 years old & they have gone off sitting on the shelf, a fired piston
from 30 years or more ago will retain it's shape & size much better then
some of the
said old but new pistons, furthermore as for the 4.2 engine blocks the 3.8
engine blocks rust inside & between the sleeves, one must do some careful
appraisal of the new 3.8 pistons to be used, then give as rule of thumb
extra piston to bore clearance how much more is dependant on a few things
but generally it's .002" more then recommended.

When one has the sleeves removed from either the 3.8 or 4.2 engine block and
new sleeves are fitted, pressed home to a machined stop at botton of
prepared, honed to size engine block cylinder, a torque plate is used for
boring/honing & the main bearing caps fitted & torqued then one could run
tighter clearances. ( by stepping the cylinder block & pressing the new
sleeve home ,the sleeve can not move down & away from the top of the block)
Jaguar never stepped the cylinder block, if they had some XK engine
problems would have been fewer, Jaguar however went to great lengths to
have fit the sleeve parallel with a good interference fit, this can not be
done as easy to day , cylinder sleeves now have too rough a texture on
outside of sleeve, like a big thread all the way up the outside of the
sleeve, this means that the sleeve only locates on the highs, engine shops
then use gunk to seal off, stick the sleeves, the latter does not give a
good heat sink & also the sleeve is prone to move down, settle and the
latter allows for the head gasket to leak.
Furthermore, Engine shops do not hone the block to size to receive the new
sleeve, they generally use an off tool finish, this with the said new
sleeves makes for a bad fit that with the gunk used causes hot spots.

The best engines cost more but it's worth doing the job properly, have the
new sleeves ground on a centreless grinder to give a smooth surface finish
, have the engine block honed to correct size to enable a true parallel
interference fit, step the block, use a B or C section sleeve ( this gives a
stand alone seal onto the h/gasket, C is better) flanged sleeves take lot's
of extra work to fit properly and mostly they don't get fitted properly, one
can not see how they are fitted because the flange hides it, I don't like
flanged sleeves.

There are some excellent forged pistons for XK engines, they do not have to
be for race work and can be as low a 8-1 compression, Venolia make nice
pistons and they will give you the compression you ask for, 8.7-1
compression is Maximum I will now use for XK engined road cars, always take
into account the amount of metal that has been removed from head & or engine
block, use 8.1-1 and you will be safe.( Forged Piston to bore clearances are
not mentioned in this Post)

When extra piston clearance is given depending upon the make & type of
piston rings mostly std. recommended ring end gap must be adhered to, I use
file finish compression rings in all top line engines, this insures better
compression & better longer engine life.

Oil control is made easier by multi segment oil control rings, Noah's cast
iron one piece oil rings can not cope with the oil control job within an XK

I like to use a Single Moly top Comp Ring, not a Chrome ring, 2nd ring I
like a plain cast iron ring.

For engine with doubtful bores I like to use a barrel shaped Ductile Iron
Top Ring & a square face torsional, cast iron 2nd ring, multi segment oil
control rings.

I don't ever now use the gapless type compression ring as it's a nonsense as
static blow by has no affect on real time engine operation, the ordinary
torsional ring with square face is fine for good bores. (gapless rings are
when used, fitted to second ring land only)

There are many types of piston rings & it can be a confusing job to select
the type of ring to use, best known brands are the safest bet, Hastings,
ACL, are just 2 I like to use, in OZ there are probably more piston ring
types made by OZ, ACL that suit Jaguars then any other maker, the ring is
selected by bore size and piston ring land sizes. 4.2 engines are lucky as
they have a bore size the same as Holden inline 6 cylinder & the 253 V/8,
makes excellent piston rings for these engines as the said GM engines are
used for many Race Cars, such as HQ classes ACL makes File finish rings
suitable for 4.2 XK engines, also have good variety of rings suitable for

ACL does not make a good fitting h/gasket for 4.2 engines it fit's badly
like the
Payen Gaskets, overhangs into the cylinder causing firstly hot spots, then
the dam things come apart & leak.(overhanging gaskets can cause detonation)
at least the fire ring cracks & the gasket blows & or leaks.

Payen have now identified that my complaint for the last 30 years is factual
they are currently looking into a new or modified gasket, believe it when I
see the gasket.

Well we are a ways from HD8's but one thing leads to another and there is
plenty more that can be discussed about XK engines on this great list.

I have hoped for many years that there would eventually be some excellent
quality engine parts available for XK engines that enhanced longevity &
performance but after many years we still have inferior h/gaskets for 4.2
engines. There is one good thing that is often sadly overlooked that is the
US made Gran Turismo Oil Pump, the said is about the best thing one could
ever use in an XK engine. Saddens me that in 2002 there is still not a
proper fitting composite h/gasket for 4.2 engines

There has/is been some rubbish parts dished out for XK engines & many
unfortunate recipient XK engines never have a chance to show their true
potential, engine shops & Jag repair shops mostly just keep on using crap
with the mentality of it's just an old Jag or worse the thing will never be
driven very hard.

One can make a good serviceable engine from a pile of s/hand parts it's just
care & fit that make the engine work but realistically an engine assembled
with good components is going to be a much better thing, where to get the
good bit's is still the problem it was 30 years ago, pity that after all
this time that atleast one could have 25% of what's available for say a
given Ford engine, guess it's that Jag owners are not too fussy or they
don't really know too much about engines.

There is enough XK engines being played with around the world to
substantiate investment by component makers but there is still not enough
good gear, good quality parts being made, Rob Beere is one person who knows
only too well what I'm saying, he does good work and hunts around to get
things made to enhance reliability within the XK engine T/chain Dampers made
for last few years are generally crap, Rob realised this and now gets them
made to his exacting specs, however it's a tough job to get better things
made for XK engines if people don't get wise & it's a near impossible task
if there is no push from Jag owners.

3.12.1 - Fitting a 4.2 Engine in a MK2 or S-type ( Terry Handley,  November 25, 2003 )

"Fitting a 4.2 engine to a Mk2 and or an S Type makes some sense,
firstly 4.2 engines cost less to overhaul and because of the vast amounts of 4.2
engines made there is a lot in wreckers, breakers and even in Jag Lovers back
yards to choose from, some model 4.2's are better then others and the
differences between different models are vast, at the end of the day they are all
good enough for all but the fastest race cars, then there is some things in
favour of just a couple of engine blocks & it's not the short stud

Whichever 4.2 engine is chosen to fit to a Mk2 there is only a few
differences that can make fitting to a MK2 from very easy to a little
tricky, the only real snags are the Generator Mount, alignment of the
Pulleys for w/pump, harmonic balancer, always use the 4.2 Harmonic
Balancer and figure out the alignment problems, the 3.8 balancer is not good
enough even for a 3.8.

If one takes a 4.2 Harmonic Balancer & Split Cone to say Ross Balancers
in Sydney they should be able to quickly mod a Balancer from another
engine, the Australian Designed and made Cyco Industries marketed as a B&M
works fine but is now too expensive as it goes from OZ to the US and comes
back here too expensive, there maybe some stocks in OZ but generally too
greedy stockists bung to days prices onto it even though it has been sitting
around for a few years.

The one thing to keep in mind is the early 4.2 as fitted to the 420
sedan & Mk10 4.2,ser 1 E Type has the larger casting for the water pump but
retains the same size w/pump impeller, the advantage is the larger dia intake.

I have built many 4.2 engines with the 3.8 pump and timing cover, 420
timing covers will fit, same pump impeller size as a 3.8 , see my cooling
system post.

The B type 3.8 cylinder head can be fitted to any 4.2 engine, when
fitting to the later 4.2 engine blocks the 2 water ways at the back of the
engine block need to be tapped out and plugs made from threaded bar or bolts
screwed in by a slot hack sawed ontop, use a loctite product, if ever
theyneed to be removed a small amount of heat in that area softens the

A B Type head with the ports taken out and metal removed from under
the valve seats works very well, but good B Type Heads are getting hard to
find, don't discount a 2.4 head it is usually in better condition then a 3.8
and there are many sitting around on 2.4 engines digarded many years ago,
only the ports need to be taken out or run it as is for torque like a Mack

A S/Port Cylinder head from the many jag model sources can be fitted to
any 4.2 engine.

For most uses the 420 or XJ6 engine inlet manifold is easiest ,a 240,
XJ6 Ser 1, 420 , 2 x 2" SU's work well enough for all but the Cars that
owners are looking for the mostest, a good 2 x 2" SU set up can beat an
ordinary 3 x 2" SU set up.

Proper porting of the 2 X SU Manifold can flow more then enough.

One little snag that's found out often at the last hour of the
conversion is the Water Outlet from any S/Port Inlet Manifold does not match up to
the MK2 radiator,when one looks at the problem it can be sorted out relatively

The down side of fitting the 3 x SU's to a RHD MK2 is many, one has
to overcome the fact that the Clutch & Brake M/Cylinders are right in way
of the Inlet Air Cleaner, that is a Filter system needs to be used and the
rear most carby is so close to the Clutch M/cylinder.

The other major problem is the inner guard needs to be modified to get
the needed clearance to fit a proper effective air cleaning system.

The beating cutting of the inner guard area causes warping of the
mudguard unless real care, expertise is used. the gap between the bonnet and
the guard becomes greater as it's pulled down once the inner area is
played with, it's usually bent down bad enough from years of mechanics leaning
over top of the mudguard.

Use the 420 Air Filter assembly it works well enough, there is nothing
to be gained but noise using anything else.

One can duct cold air through the N/S inner guard and hook it upto the
420 air filter, early Mk2's had the hole there for the fitting of a Tube to
the under N/S Air Filter that was used on some export models, many MK1's
had the said, make sure you continue the pick up to a position up front rather
then just picking up air from under the mudguard.

You can see the proud area of the inner guard where the connection was
made, it was blocked by Jaguar on some early model MK2's & then later
pressings, the hole was not included.

Obviously I have only touched on the surface of fitting a 4.2 engine
and the possibilities are numerous many listers have done and are doing this

I have found that a well prepared, slightly modded 4.2 engine with 2 x
2" will still to day surprise many a modern car driver, recently I had
the occasion to let loose a Slightly modded 4.2 MK2, it was only the aged
tyres that made me back off & let an XR8 Ford Falcon go buy.

Make no mistake a modded MK2 4.2 is still today a very fast car that
can embarrass even GM & Fords supposed Quick Road Cars, you can see this
when Normie turns up at Oran Park with Holden.

A 3.8 engine needs to be modded a lot to perform as well as even a
standard 4.2 engine performs in a MK2, the extra torque of the 4.2 means a lot
more grunt without the down changes, quicker acceleration more power up the
hills, near forget 1st gear.

A 4.2 engine with a safe low compression of 8-1 goes harder then a 3.8
with 9-1 + Compression and it will run nicely on lower grade fuels.

A lightened Steel Flywheel & a 9.5" Clutch on a 4.2 livens the engine
considerably without affecting tractability.

The later XJ6 Engines are heavier then the early 3.8 engines and the
extra weight can be felt at kerb speed, however the standard MK2 Springs are
really too light for even a standard 3.8 engine so an update to at least
1000lb Front springs is needed for a MK2 that does other then sit around.

In a Racing MK2 you need 1600 lb front springs, I like 1200 lb front
springs for my road Mk2's and use a Front Anti say Bar from a 420, a heavier
bar gives too much understeer for a road car, that is unless some other
thingsare not done to make the MK steer & handle better.

A MK2 with heavier springs suprisingly does not ride too hard, most
new sporty cars with the low profile tyres ride more harshly then a modded

Obviously there are many aspects of a 4.2 engine conversion that can
be talked about on the List but simplicity for most is the key to a good
reliable fast MK2, often lot's of money can be saved by buying
scrapped 4.2 engines and pulling them down and building one nice engine.

Mod the head & inlet manifold, fit the exhaust headers that allow the
fitting of 2" od primary pipes some Headers are not large enough inside
to realise the benefit of the said primary pipes.

Avoid fitting Tube Type Headers with larger then 13/4" OD Primary pipes
you will gain nothing but heat and lose plenty of power, biggest is not
always best.

One can use the standard MK2 exhaust and a 4.2 engine , still gives
more useable power then the 3.8. Don't believe the myths about a 3.8
engines being faster, those early 3.8 E Types when compared to later
Ser 1 4.2 E Types had gearing advantages and lighter flywheels the
4.2 engines usually had the heavier flywheel.

Bring the primary pipes into one 2.5" pipe from about central position
of the g/box through to a Walker or Lukey Free Flowing 2.5 in & out
muffler and on the outlet siamese to 2 x 17/8" Tail Pipes, this set up
gives a nice note and flows enough & better then a standard MK2
twin system and it's not too noisy.

3.13 - 4.2 head swap to an early engine ( Paul Saltwick,  December 17, 2005 )

Are you aware that the MK2 intake manifold cannot be used on a
straight port head ? You will also need a 340, 420 or XJ-6
(Euro) intake manifold for this swap.

The problem is the rear intake cam bearing cap, the S3 version
Is not made for a tach generator. The cam bearing caps are line
bored and generally should not be swapped around. The rear of the
head is also not machined or drilled and tapped for the tach
generator bolts. If money is no object, swap the cam bearing cap, and
have the head line bored, spot faced and drilled and tapped. You
could try to shim the rear cap underneath or underneath the bearing to
come close to the proper clearance and alignment, but I don't
recommend it.

The best compromise for the benefits of the S3 head is to change
the tach to a 420, S2, E, or XJ-6 S1 electronic tach.

Using the later cams in an early head is not a problem. The
rear of the intake cam is plugged with an aluminum plug. Drill a
1/8'' hole and pull out the plug with a screw. Tap the cam for the
tach drive thread, then increase the angle of the chamfer to match
the tach drive. Unplugged both ends and rod out the cam while you
are in there, it is the oil galley for the bearings. Assemble
the head without the rear bearing and shim the tach drive to the
same clearance with the factory ''C'' shaped shims.

The early cam covers are easy to fit. One of the factory half
moon plugs will fit the exhaust side. Make a plug for the rear
opening on the intake from 1/2'' Buna rubber using a 2'' hole saw, then
split it in two. Use the later S3 gaskets, they are much thinker.

3.13.1 - Fitting a XJ6 4.2 water pump to a 3.8 ( Paul Saltwick,  March 11, 2004 )

I know this has been covered before, but can someone remind me which version XJ6 timing cover do I need to get to use an XJ6 water pump on my 3.8?

Hello Niels,

As usual, it depends. There are at least four different XJ-6 pumps, so you are better off getting a timing cover that matches the pump, all the timing covers will fit the block. The problem will be the radiator clearance and the fan. I think the last pump with the final improved impeller and larger bearing (S3) is too long for a small saloon and the pulley shaft is larger so you can't refit the original pulley. For the XJ-6, Jaguar increased the impeller diameter and thickness (3.04" vs 2.75" and 0.625" vs 0.5312"), improved the seal to allow higher pressure and increased the pump speed from 0.9 crank to 1.25 crank speed. Apparently, problems persisted and they improved the impeller again
and uprated the pump bearing and seal again and used an even smaller pump pulley. The best compromise for a 3.8 may be a mid XJ-6 pump and timing cover with the S3 crank damper and pulley. An old timing cover can be milled out, the dimensions should be in the archives. You also need to make a hose pipe adapter for the lower hose.


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