ORIGINAL: Jim Oliver

The small case (.46 size, according to Dub) has a shorter crank throw, which means less torque, which limits the small case engine to lighter props (less prop load) than the big block engines.

That said, there are some of the smaller, lighter Classic pattern models than can use the small case 60 very well. The original Kaos, Super Fli and others of that size and weight are better powered with the small case 60 than the much heavier big block 60. Be aware that an 11x7 prop is a heavy load for those engines.

Years ago, folks trimmed props to 10 1/2 dia. and maybe slightly shorter, to get the rpm & flying speed desired, when using the early smaller, lighter 60 size engines.

Just match the engine to the airframe and all will be OK.

Jim