I have owned my RV-10 with a 260 hp engine in it for 11 years now and it has been great. I have put 1,300 hours on it so I am no where close to TBO BUT I thought, wouldn't it be nice to have some more horse power for those high density days and flying out of the mountains. Not crazy horse power because more HP leads to more heat. I was thinking about a Lycoming with 300 hp. I know that they make them but the question is, will it fit? Has anyone put a 300 hp in their RV-10 and if so, what model was it. When talking to Lycoming, they said to go above 260 hp you would need a angle head engine that might be wider than the regular 260 hp and they wondered if it would fit in the same cowling. I am well aware of the heat issues and the VNE of 200 knots TRUE airspeed. I am not doing it for airspeed but as I said for mountain operations and high density days.