Of engines I have had, my (2) O.S. .40 FP engines ran perfectly and never gave me an ounce of trouble. As far as power, it was a little weak on my PT 40 trainer but my Falcon 56 was a rocket with this engine. I had a Magnum Pro .45 that was also an excellent engine that had massive power! It spun a 9X6 prop so fast it would shatter a nylon prop. I had to use wood props to eliminate the flattening of the pitch that would cause my props to shatter. I had my Scat Cat Pylon racer clocked at 127mph with this engine.

However, the first engine I ever bought was a bad apple. I bought a K&B Sportster .45. This thing is a boat anchor! I never could get this thing to run right. Even the senior rc guys could not get it to consistantly run without flaming out. I almost quit the hobby out frustration because of this engine. I gave it to someone and bought an O.S and my problems were solved. The thing is, my friend had an old K&B .40 engine and it was very reliable. I still will not ever buy a K&B engine again.