In answer to Kim S, the Chapman diesel deserves a thread of its own.
The diesel was first made in 1933. Over its production life, into the 1940s, it was made in 10, 15 and 20hp. The 20 was a twin.
A compression ignition engine, it was started with petrol at low compression. It was never advertised as being reversible. A reversing gearbox is shown on the accompanying image.
So far I have not heard of an existing engine.
Eric