Maybe someone fitted a long reach plug by mistake?
Whatever it was, there's no sign of erosion and not enough damage to affect how the piston rings will seal.

As for tidying up the bores, 'old school' style here...

http://www.youtube.com/watch?v=uJqMdZ2IB7s

ken

p.s. @ Smiffy. I always leave that ring of carbon at the top of the barrel as it is.

That is my opinion too.
The barrels do'nt look that bad, so maybe it is worth saving the old parts.
I don't think the "dent" will affect the reliability of the engine.

But the question remains: "In what condition ist the cranck?"
I am afraid you will have to split the engine completely, which I did and I really did not find it very hard to do, I kept "How to restore citroen 2CV " at hand to prevent to make a mistake.
It is like a cookbook

Just split the case and had a look inside... when I looked inside it occured to me (duh!) that I hadn't got a clue what I was looking for!! I took some pics (I'll upload later) and everything looked fine to me, but I need some pointers from you experts with regard to the telltale signs of what constitutes a knackered crank.

Count me out, I just did it once with the cookbook at hand

B@gger,
if I'd noticed this earlier, I'd have advised against splitting the cases, as putting things back together correctly is always more difficult than pulling them apart.

A preliminary test of the crankshaft would have been to check for any 'in & out' play of the con rods, as it's invariably one of the big end bearings which fails first.

Mind you, now that it's apart you can do the definitive test which involves suspending the crankshaft in one hand and striking the top end of that con rod with a gloved hand.
If you hear a definite 'clack' noise, there's play in that rod's big end...

Also check the camshaft for wear on its lobes, most common on the ramps of the exhaust lobes for some reason.

There's some good descriptions and pictures of how to check the crank in the technical forum, from when I was asking about it. My advice is don't check it, you might be disappointed.

It is a chance to clean it all up 1
i was glad I did, because there was so much sludge in my engine and now I could clean it all.

You only should be carefull when putting everything together again.

Opening the engine case was an interesting and satisfying experience. After removing the various nuts and bolts, cracking it apart felt rather like separating the halves of a chocolate easter egg!

There was a load of sludge at the bottom, as I expected, which all cleared away after a quick dunk into a bath of petrol. Everything moved freely and I couldn't see anything horrid - although I'm going to have to go and look up the whereabouts of con rods, big end bearings, exhaust lobes and so on in order to know for sure.

Here's what I saw:



Putting the case back together was interesting. The crank wouldn't turn when I tried to tighten the case (the two halves were very reluctant to mate together), so I loosened everything off and will leave it with a slight gap for now.

No wonder I can't find any decent feckin' rear doors for my van, moan droan etc.

Got fed up with faffing about with a ropy 30-year-old toy welder (Clarke 100E), so I sold an asset or two and bought one of these!