When I was thinking about this while posting something in the steam car thread, I had a short list of auto and aero engines for the best
1) SBC in particular the 1970 302
2) The Cosworth 4 cam V-8, the greatest racing engine ever designed, sorry Offy fans
3) The Porsche 6
4) The Honda Four cylinder, in particular the S2000 motor
5) The AMC Inline 6, Think of it as an inline SBC. The bore centers, deck hieghts and a lot of other things are very close, handicapped by crappy induction systems for most of its life. Still in production
6) The Jag 3.8/4.2 Six. Fot the sound if nothing else
1) The P&W R2800, its been called Pratt and Whitney's reliable masterpiece
2) The Wright Whirlwind, the engine that really proved the radial concept IMO
3) The Merlin, what does one need to say
4) The DB 600 inverted V-12
5) The P&W R4360, The most powerful piston aero engine to ever go into large scale production and arguably the most complex ever to fly in terms of number of parts.
6) The Sabre simply because of the daring in the design
Might of beens
1) The Wright Tornado, 42 cylinders of liquid cooled radial with plans to go to 70 cylinders. Never flew
2) The Napier Nomad. Ambitious in design but overtaken by the technology of the gas turbine
3) Lycoming's Monster 36 cylinder Liquid cooled radial. Simply the largest piston aero engine ever built. Never flew
4) The Rolls Royce Crecy. Like the Jag for the sound in nothing else. Never flew AFAIK
The optimist says the glass is half full, the pessimist says it's half empty. The paranoid in me says somebody put a hole in it.
Remember pessimists are at heart opptomists. They know things can and will get worse.