Ha was doing this last night and taking pictures
not much to add to Kens post.

weigh the pistons and gudgeons and circlips as a set juggle them about till you get to the closest match and then adjust the heavy piston by carbide burr inside the skirt but beware you make a scary amount of alloy swarf to even get close to loosing a gramme.

pistons i weighed last night were a perfect match

as for the 9:1 i think i used all mine up ( fekin' kent cam)
but a good set of barrels and rings and youd be hard pushed to tell the differance from the drivers seat.

if you've got a hone give it a quick tickle on fast speed in the drill it'll polish the high spots and indicate the areas of wear if you can see the wear ridge or feel it have a look for other barrels
new rings! not even up for debate

and look for pinking damage look on the underside of the piston usually the skirt dragged up into the oil cotrol ring or the land between the comp rings nipping the ring

popping lid:- timing too advanced and tappets needing adjusting?

Sean

Could a knackered breather make the air filter pop up from positive pressure inside the engine making its way up the pipe to the air filter box?

Popping lid -

On mine I just changed the breather, will check timing and tappets...TA for advice.

Just wondering
What mods can you do to a standard 602cc to get a bit more power. Dyane pistons.. And...?

Citroen spent a lot of time/money getting the set up right, just leave it alone, give it regular oil changes, and the engine will go well beyond 200,000miles.

Now this is a very intelligent comment.

not a lot unless you start spending silly money

the easiest is sticking on 9:1 pistons and new barrel set. but that's not much really some engines just fly others are a bag of spanners.
One of the theories is its all how the cam timing gear wheels were attached, some were just right others were out - if there is a tolerance for the crank and a tolerance for the cam -combined there could have been enough to affect timing. A late friend had a race engine that was brilliant (Now owned by last years championship winner)-that D*lly that comes in to me has an engine that I want, even on standard pistons it has so much grunt( supose i should of checked it when it sat here for nearly a year)
Dyane cams are the same as 2cv as far as i can deduce from part Nos

Uk racers have started using vernier wheels on the cam

if you can get stuff machined then taking a skim off the top of the barrel increases compression
Then you can fiddle with exhausts inlets and carb jets.

or you can make 652 hybrids

But for day to day stuff just screw it all together nicely and take your time setting everything up just so

As Sean said there are tremendous variations in how individual engines run. I think the "Citroen spent a lot of time" line isn't really entirely true. The cars were thrown together any old how and as long as they sort of worked everyone was happy. Most only ever got pottered round town anyway.

Before you start improving you need a clear idea of what you're trying to achieve. Better fuel economy, more low down torque, more top end power; some goals are mutually exclusive. It is just an engine, it'll respond to higher compression or improved air flow or more fuel or more valve lift but as the racers have proved with the Kent cams there can be a trade off.

There's two issues being mixed, I think. One is the design goals, the other is the build quality.

It sounds like James wants to revisit the design goals - and make an "A-series gt", which Citroen never built (well, they did - the Ami Super!).

Build quality is almost irrelevant now, since few 2cvs haven't had at least some restoration or rebuild work since being built, so the relevant quality is that of the later work...

My take on it isn't so much that 2 issues are getting mixed, but there is a natural progression. As ever with "tuning" work the hard part is knowing where to draw the line in the sand. Many an expensive trick engine has been built that was horrible on the road and wonderful on a dyno.

The start for good tuning work is optimising what is already there, you get the cam timing just right, remove casting marks, match the weight of the pistons, equalise the combustion chambers, lighten flywheels and remove some of the safety margins any manufacturer builds into their product to prevent it grenading when an owner doesn't change the oil or air filter for years at a time.

The basic tolerances tend to just be taken for granted when mild engine work gets done to cure a leaking head or burnt out valve. Even when pistons or barrels get changed the majority of us just clean off the transit oil and fit them. Most engines will benefit from careful assembly, essentially basic blue printing. This work is cheap, if you do it yourself and time consuming if you pay someone. It also has lots of scope to completely balls it up.

Going beyond that there are hotter cams, STP in Germany for instance have them, they also have big bore kits, stronger push rods . I have no personal experience with them. I've never felt the need to create a screaming 2CV engine, so I'm pointing out it exists, it isn't a recommendation! http://www.citroentuning.de/n_2cv.php

http://www.citroentuning.de/tuning_e.htm

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