I'm told that coking is pretty normal, I was surprised when I
dismantled an engine for the first time and found that three cylinders
were black with soot and coking while one was clean.  As it turns out,
the clean one was the problem as its very cleanliness demonstrated,
washed by a coolant leak.

As for compression, if you've got a step in the bores then that
signifies wear, which if it's large enough it could cause exhaust
gasses to get into the crankcase (as it did in my case) but I'm not
sure if that's enough to lead to a drop in compression.  The bores
becoming oval through wear might do I suppose.  I used to get a lot of
oil in the air filter, it was coming up the crankcase breather hose
into the air system and being sucked as mist round to the filter, this
was happening due to the exhaust gasses blowing past the cylinder into
the crankcase.  This was on a non-landy engine though.

Hopefully someone will tootle along later on and know your particular
model of landy engine well, all the above is just FYI.

Was this a general loss of compression on all cylinders or on one/two
cylinders only? Remember that there is not much compression on these
things, anyway. What was the reason for strating this investigation?

Whilst you've got the head off why not inspect/grind the valves? I've
had two cases of chunks out of exhaust valves. This whole area is
another potential compression loser.

I don't imagine that the wear in the bores is anything to worry about.
What you describe is fairly normal when a few miles have been
accumulated. As long as all cylinders are equally oily (preferably not
oily!) you can probably also rule out broken piston rings. Any other
symptoms like burning oil or high crankcase pressure?

Is the blackness oily?

First, do not use a chisel, screwdriver, knife or any other sharp tool
to get the gasket off. I've found that a Dremel-like tool works best.

Second, make sure that you take the head to a machine shop so it can be
milled. Anytime, cylinder heads are removed from the block they will
warp. Explain any damage the machine shop and why you removed the head
in the first place. More they know the better the job you get.

Third, use the highest quality head gasket available. I have always had
success with copper shim type gaskets. Those are generally found on high
compression, supercharged and turbocharged engines.

Fourth, run a straight edge (such as a machinists ruler) across the top
of the engine block. You're checking for any warping of the block
itself. You may [or may not] have to remove the block for the shop to
work on it.

I started off with the hairy stuff at first, Eh? You didn't mention what
the engine was, petrol or diesel. If petrol, any backfiring? If so,
fouled plugs, ignition wire gone bad, distributor/rotor needs replacing.
If diesel, a lost of compression through a fault in the head gasket, oil
blow by on the piston rings, timing belt/chain out-of-wack.

If you have a diesel and you're close to a seaport, such as I am here in
Norfolk [aka Hampton Roads] Virginia, a marine mechanic could be quite a
bit cheaper than your local Land Rover dealer.

Sorry, folks but the local dealer has tried to rape me when my wife
brought hers or I brought mine in. My son learned from my experiences.
Just my quid's worth of knowledge.

Cheers.

That's not terribly inusual on engines of that age, indeed de-coking
used to a fairly routine operation - hence top-end sets are often
referred to as de-coke sets.

The 2¼'s will take a fair bit of abuse, so a step is not the end
of the world - it does need to be measured though to check it
is in tolerance. Look of the sides of the bores for signs of
blow-by, i.e. gas passing the piston rings. Black/discoloured
"scorching" indicates ring/bore problems.

While you have the head off, strip it down and check the condition
of the valves and valve seats - there should be a nice shiney ring
round the valves and a corresponding one on the valve seat - any
"gaps" mean the valve is not closing properly which will give
low compression. Also check the valve guides for wear. The Haynes
manual gives the required info. Having got that far, you may as
well get the head skimmed. Also check the condition of the
rockers - particulary the bits that make contact with the push
rods - and check the push rods (roll them on a flat surface looking
for kinks). Also have a look at th valve springs - line them up on
a flat surface an see if they are all the same length. The springs
are not over-critical on a 2¼ pertol, by one school of thought
says replace them anyway having got that far (94p each).

Assuming all is well, and you intend running the engine again for
a while, you might consider having "unleaded" valave seats put
it while the head is away - not least as you get to avoid lapping
the valves yourself that way!

Richard