This project is so amazingly bonkers, I love it. It's a home-built radial engine, which, as far as reciprocating engines go, is clearly the most exotic. And, it's built out of engine parts from the air-cooled flat-4 of a VW Beetle.
The guy who made this, Arnold de Man, seems to have done a fantastic job. The seven-cylinder radial was built from parts from a VW 1200 engine, which means it displaces 2086cc. It's got a double Solex carb and an awful lot of custom-machined parts.
What is a mystery is the end goal of this engine. Is it just an exercise unto itself? If so, that's totally worth it. Is it going to power an old airplane, like most radials tended to, or will it get shoved into some car project, which would also be amazing? It seems to be a pretty compact power plant, and if I had to guess I'd say it may make between 80-100 HP? Maybe?
I'm very impressed. Even just looking at how radial engines work makes my eyes cross a little bit.