What about engines other than aircraft? Maybe, like motorcycle engines? What about motorcycle engine porn?
I came across a pic of an engine about 2 years ago I had never seen before. It was by far, the most beautiful engine I had ever seen! It was very old, not very big, but extremely stylish. The cylinder and head assembly was kinda tear drop shaped as was the crank case. It was in some kind of small displacement bike that was likely European. It was drop dead gorgeous. Art! I don't remember what the heck it was, can't find it again and lost that copy of the pic with a hard drive.
The Rotax 605 was in a few bikes I really liked for a time and we're used in many racing applications...then they vanished from existence. The SOHC version had a solid reputation. The DOHC not so much.
The KTM 640 was another single that was kicking around for some time in the same period.
The engine in my latest bike is nothing to look at, though I admire its lawnmower like simplicity and reliability.
I've gotta respect anything that's been around for a couple decades with little to no changes.
I've always had a thing for the Ducatis. That's easy.
One of my criteria for ownership (as it tends to be a long term affair) is ease/cost of repair/rebuild. They're among the worst on that point.
Here's one I found on Youtube. I read an article about it in an English magazine. It was probably in th 1990's. Anyway, this guy cast cases for 5 & 7 cylinder Kawi triples. He actually ran the five sets of points in the already tight points case where three sets were housed. I don't remember the points case on the seven cylinder but imagine it to be horrifying. One of the bikes actually displaced 666 ci. The best I can do is post the link because I'm a retarded caveman, sorry https://www.youtube.com/watch?v=_hn9LidVa6g