james, thanks for the info. i neglected to mention that i have a prather mod kit on my motor. but, after blowing the rod out of it yesterday, i nedd another prop for my stock motor. i have a prather 215 ss that i like, but i feel that it loads the motor too much. it is a stock k&b 12mm crank, perry carb with the head set at .010". i run 30% nitro/20% oil-syn/castor. any ideas? x440 still good, or maybe down to a x438? i know where i can swap for the x440. any help will be appreciated.