Converting the Webley Senior from a piston ring to a leather seal?

[felix gunner]

The relevance is that both Webly and diesels use rings to achieve the same task, ie building up pressure rapidly. One caveat for metal rings in both instances is that the bore must be perfectly round and not scored to achieve a perfect seal.
Leather/synthetic seals are more forgiving in this respect as they adapt and swell to fill any imperfections in the cylinder.

Hmmm, I think this is being dragged off topic but maybe the use of a ring (single in the Senior) that happens to be split is as much of a similarity as it gets. The ft is much tighter in an engine, oil is a critical part and there are usually three of them.