The 4 cylinder on the left is an Aerovee 80 which is a converted Volkswagen Beetle engine commonly used in Sonex aircraft. In the middle is a generic radial, it isn't really based on a particular engine. Thats actually the full detail version of the one on my Barnstormin Biplane. The one on the right is a single cylinder 2 stroke, sort of a hybrid between a Hirth F33 and a Rotax 277. They are to scale and have fairly accurate masses. I am a nerd for anything mechanical so I really like making these.

If you want to save one as a subassembly the 2 on stands can be removed by taking off the 4 fuselage cylinders that attach them to the stands. For the 2 stroke just grab it by the orange cylinder. Make sure if you scale use the relative scale option or some wacky things may happen, especially with the radial. I tried to make them as easy to use as possible but with so many parts wierd connections can happen.