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
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?
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.