Swarfy,
Right! Well there were at least two problems and the rings were certainly one one of them. The symptoms, the methods and the solution to the rings problem are all in the thread in some detail, so if I concentrate on the second one...
... the delivery volume from the SRM pump is massive and will fill the crankcase at tickover in less than 5 minutes if left unscavenged. So if there is any weakness on the scavenge side, perhaps an airlock somewhere or (as I think in my case) a scrap of PTFE tape partially obstructing an oilway, there can be oil everywhere except the tank, and in very short order. That's about the best explanation I can give.
The lesson I have learned is to blow everything through with compressed air immediately before assembly, and be extra vigilant when using PTFE tape. I am a fan of PTFE for sealing threaded joints, and had used it on the union between oil return pipe and the tank. When going through the system with the air line I found a "tail" of the tape was actually in the pipe. It might have impeded the flow. Can't say for certain though.
Now then, anyone got a '54 Rocket for me to play with?
Steve