A friend was getting out of nitro planes into electric stuff and I got some stuff from him. With the stuff was an Evolution engine on a 40 size plane. The engine was filthy so I gave it the old antifreeze-in-a-crockpot treatment, oiled it up, and flew it today. It was an absolute delight, performance wise. Impressive would be the word. The only bad thing about it is that nowhere on the engine does it list a size. I assume it is a .40 to .55 size judging from the plane it was on, but I am not sure. My question is for you Evolution enthusiasts out there: how can I determine the size of the engine?