[Glenn from Denv]

Nice work!

I've got something similar in my RSR motor (although I am using copper for ring material).

My solution mates the head to the cylinder using the flame ring. The ring is shaped a bit to help with the sealing. Think of your ring with a groove cut out of the inside edge. The side with the larger inside diameter (thinner "wall" thickness) goes into a properly sized groove on the cylinder and the side with the smaller inside diameter goes into a groove in the head (like yours).