Many engines can converted to Rc airplane engine, I have some. Poulan 46 is ideal, it is almost ready engine, just make a prop hub and go to fly, with a bit of work you can converted a Homelite 25 cc mine turns a 18x10 APC 8500 rpm. take a look to:
http://www.shark-racing.com/Ingles/T...acaoMoting.htm