I've finally got around to rebuilding the engine on my 2cv. One of my first jobs is to fit new barrels and pistons. I didn't think it was going to be particularly easy but I didn't think I would be asking the question below.

I've had the new barrles and pistons for about three years (perfect circle 9:1). I've been trying to find out the position of the rings. On consulting the Haynes manual I've learnt that the barrels and pistons are matched at the point of manufacture. Well, of course, having admired these wonders of engineering over the years I've no idea which piston was matched with which barrel .
Secondly, Haynes says that the pistons are handed with an arrow pointing to the front of the engine. Indeed the pistons do have an arrow marked AV and below is a g in lower case but they are both marked with a g (one of the gees being quite wonky, looks more like a g than a d though). I don't know if this g refers to gauche or just a random letter.
I'd be very grateful for any advice/comments.

Rings dont matter as they rotate in use I usualy go with 120 deg withgaps toward top any mark on ring goes to top if 2nd has a cut out thats down
Arrows point to front and the g is a 9 for the comp ratio
Sean - by phone from work

Steve H,
the need to 'match' pistons and barrels suggests poor quality control, rather than the opposite.
As far as I'm concerned, it doesn't apply to replacement piston and barrel sets.
I've put the micrometer over a few sets and there was no significant difference between the sides.

When fitting new rings to an engine, I'd always keep each piston with the barrel in which it's been run, but that's a different consideration.

Are you sure that the characters/numbers below the arrow aren't "9.0", to indicate the compression ratio of the pistons?

ken

Thank you Sean and Ken for your very quick responses.

Yes, the 'g' is indeed a 9. I was just sent down the route of left and right handed pistons because of the info. set out in the Haynes manual!
Thanks for your comments Ken on the need (or not to) on the matching of barrels/pistons. I can see the need to match on pistons/barrles that have ben used with each other before but not on new.

Well thats that query sorted.
My next concerns the rings. Thanks Sean on the spacing but I'm afraid that's jumping ahead of me!
There are 5 rings per piston. I was expecting only 3.
I have 1@ approx 2mm (sorry I was a wood butcher not an engineer)
1@ less than 2mm,
1 which I can only vaguely liken to a spirally type jobbie (which I'm assuming is the oil ring which goes in the bottom groove?)
and 2 remaining rings at around .5mm.
If I'm right in that the 'spiral' type jobbie is the oil ring and goes in the bottom piston groove, the 2mm goes in the middle groove (as its too thick to go in the top groove), the less than 2mm goes in the top groove where do the 2 thin rings go? Either side of the oil
ring?

yup

HPIM0682 by Sean602, on Flickr
click the link and youll see the other rings going in

black spring ring first then the 2 thin steels either side of it
then the thicker no 2 then top. Are the rings not already on the piston or in a little paper wallet?

Something to watch out for with those 3-part oil rings.
The ends of the segmented part have a tendency to overlap, so make sure that the ends are kept in abutment until the 1mm rings are in place.

ken

Thanks Sean for the excellent photos, a great help and reassurance. I was wondering if the piston could be inserted into the barrel all ringed up prior to fitting to the con rod. Is this the accepted way of doing it? I have to admit that I thought the piston had to be fitted to the con rod first then the barrel offered to it. Which seemed pretty tricky,unless you were an octopus!
The rings didn't come in a packet. It took me some time to find them as they were inside the barrel, they actually looked part of the barrel

Ken, thanks for your advice regarding the bottom ring, I'll look out for that.

By the way, the gudgeon pin is a push fit, though tight, ( I had to manufacture an extractor for the old one)
Thanks again Steve

As the photos show piston in the barrel first works. It will depend on your ring compressor if the pistons on the rod then when the barrel is fitted you are left with a ring compressor stuck below the barrel.

This is what I do

...while the russians send a pencil...