With the cilinder heads out, I decided on an inspection and soon found out that the valves were a bit worn in. Especially the inlet valves. Also the oil rings in the camshafts had become very hard. I made the choice to replace as much as needed now that the heads were off. I dismantled the springs, valves, seals etc to clean all the parts.
Then I brought the cilinder heads to a specialist to inspect the valve guides. They were found to be still ok.
New camshaft seals, valve stem seals and inlet valves I bought at Daniel Engelhardt’s shop. I lapped the valves in on the heads.
One thread of the inlet manifold was knackered so it had to be repaired with help of a M7 repair kit, which I did with help of 2CV Garage Sander Aalderink.