Rossi 60 or 61, YS 60, Webra 61F racing longstroke, OS 60 &61FSR are a few of my choices. All are very good/powerful engines. The one that still blows my mind away though is the Enya 60 XF series engines. It is good on power, but nothing can compare to this engine's Marathon life. IT "was" the only engine that I can truly say that if every flight was worth a penny, compared to the cost of the engine itself..... I would have a nice wad of cash in my pocket. This engine payed for itself over, and over, and over......

Another classic.... The Super Tigre G60 Blue head.