Some of you may remember that my 1969 E-Type (4.2L XK engine) developed an
intermittent misfire on the #5 cylinder a couple of years ago and that it
was a challenge for me to find the cause. I first suspected ignition, but I
was wrong, then I suspected fuel, but again I was wrong. It turned out to
be a worn valve guide and valve springs on the #5 exhaust valve allowing
that valve to wander a bit. When it sealed correctly I got good combustion,
but when it didn’t I got the misfire. Compression checks showed good
compression until one day when the #5 compression was much lower than the
others. I removed the cylinder head, saw the problem with the valve and
took it to a local shop for evaluation and an estimate. They wanted about
$1,300 US to rebuild the head (valves, valve seats, valve guides, springs,
mill, etc). Instead, I decided to use the head from my 1985 XJ6 parts car
(4.2L XK engine) that turned out to have been reworked just before the car
was junked about 8 years ago. It seems that the engine in my parts car had
never been run after the head was replaced. I had no history on the car, so
I had no idea why the car was junked. When I removed and disassembled the
head I noticed that the intake and exhaust valves had been swapped by
mistake and were in the wrong positions and that there were two belt valves.
This was probably why the prior owner or shop junked the car.
Lou Danzico, a friend from the XJ list living in PA, loaned me his valve
spring compressor and I removed all twelve valves from the head of the 1985
parts car. I inspected everything on the head and except for the two bent
valves everything looked good to me. I purchased the two new valves (about
$20 total including tax and shipping), installed them and last Friday I was
able to start the engine for the first time for a careful monitoring of
coolant and oil and for a short drive. I also had all the various intake,
exhaust and head gaskets on hand from a box of miscellaneous XK engine head
gasket kits that I got on ebay about five years ago. So the direct out of
pocket expenses for the cylinder head swap was about $20 instead of the
$1,300 for the professional rebuild of the original head. I plan to keep
the original head just in case I decide to get it reworked in the future.
Since last Friday when I first started the car I had two failures unrelated
to the head swap. 1) I had a failed 6RA starter relay (one of the internal
electrical contacts just fell off and I got a “no crank” situation) so I
swapped it out with an identical 6RA A/C relay located near the battery used
for the air conditioning; and 2) Then for some reason the condenser decided
to die and this resulted in a “cranks but does not start” condition with no
spark at all. After trouble shooting the wires, cap and rotor, I thought it
might be the condenser. I had a spare condenser on hand and once I swapped
that out the car started up nicely again.
I just came back from another short drive in my 1969 E-Type. It started up
nicely, had no leaks, and in general the oil pressure and coolant
temperatures looked reasonable.
Because I used a cylinder head from a 1985 4.2 L XK engine on my 1969 E-Type
I had to accommodate a few differences: I used the 1985 XK engine cam covers
and half moon seals at the rear instead of the original cam covers; I bolted
up the four bolt cam shafts to the two bolt holes on the timing chain
sprockets and safety wired them; I used the newer lifting brackets; I used
some slightly shorter cylinder head studs that I had on hand for the newer
lifting brackets; and I couldn’t use my spark plug wire conduit cover so the
head now has the newer spark plug tree brackets and spark plug trees.
AND IT RUNS!!!
This was one of the most ambitious XK engine projects I have done to date on
my Jaguars and it was certainly a delight to hear that engine start up so
nicely last Friday and again today. The compression check on a cold engine
before start today was a very even 146-150 PSI and I set all the valves to
0.012-0.014 inches last Friday as they should be with a newer head. I plan
to rerun the compression check on a warmed up engine the next time I drive
the car.
I will be cautiously checking things out over the next week or so to make
sure my work stands the test of time. I am still evaluating the oil
pressure as that doesn’t seem quite right yet, but it could be the gauge. I
plan to connect a direct reading gage to evaluate that further, but for now
the engine starts nicely, has oil pressure and runs very smoothly. The
misfire is gone, and my only direct out of pocket expenses to complete this
project will be the two replacement valves and the shipping costs for the
borrowed valve spring compressor from Lou Danzico.
AND IT RUNS VERY SMOOTHLY!!!
Regards,
Paul M. Novak
1990 XJ-S Classic Collection convertible
1987 XJ6 Vanden Plas
1985 XJ6 Vanden Plas (parts)
1984 XJ6 Vanden Plas
1969 E-Type FHC
1957 MK VIII Saloon
Ramona, CA
@Paul_M_Novak1
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