I had a 1954 Traction Light 15 where the valves made noise no matter how I torqued the head or adjusted the valves. What it was, was that the rocker arms were worn and loose on the rocker shaft. I replaced the shaft and the rockers and it was finally quiet.

How often you have to check the head screws? Motor of my 11cv was opened 200km ago. When I have to do this job and how often again? Is there any rule or technical information about? Thanks for this fantastic video about it. Really great and helpful..Karsten