My 1958 sidevalve Reliant, was mostly reliable. Compared to the motorbikes, I used to ride....
My party trick, was to change the head gasket, in 90mins at the side of the road. Every few months!
I cured it. By chiselling a crosswise shallow groove, in head and block, between nos 2 and 3 cylinders. It never blew again, in my ownership!