The steel ring shrunk into the upper crankcase seat area for the liner lip to sit on can be clearly seen. Also notice the front end was threaded & bolted to the crankcase. This crankcase from a 1978 OPS 67 is the only stock motor I ever tested on the dyno. It produced 5.8 to 6.2 HP on 65 % nitro at 24,000 rpm. Every part in this motor was broken at some time!
The steel ring prevented the liner from crushing the lip in the crankcase.