There are two steps to removing the valves from a 2CV’s cylinder head, you need to remove the rocker arms before you get access to the valves.
The rocker arms sit on pivots that are held in at the top by the cylinder head nuts and at the bottom by a bolt with a special head with two flats. Fortunately an adjustable spanner provided enough purchase to free them off without needing to resort to “advanced” techniques.
With the bolts removed the rocker arms come free.
The rocker arms slide freely on the pivots and there are two sets of washers on them, a thick one one at the top and a spring washer and a thin washer at the bottom.
Now to remove the valves themselves. (Not too many pictures of this as it’s a job that requires three hands at the best of times…)
First a digression about how the valves are held in place. At the top of the valve stem there are a set of circumferential grooves which match the ridges on the inside of the semi-circular collets. The outside surface of the collets has a slight taper that seats them in the valve spring retainer plate that sits on top of the spring.
As that taper is constantly under pressure from the spring and will be expanding and contracting as the engine heats up and cools down it’s going to stick so, before compressing the spring, give it a small percussive persuasion to free it.
With a valve spring compressor (effectively a large C clamp) in place and the percussive persuasion having been applied it’s time to wind in the threads. When the collets are clear of the compressor collar you can go in with a magnet and extract them.
After fully unwinding the compressor to remove the tension, the valve springs lift off.
The valves then push though into the combustion chamber and can be removed.
Finally the valve stem oil seals can be removed. With the valve spring seats removed the metal collar can be prised off which allows the seal to be pulled off the valve stem.