"I was running full out for about 30 seconds when the motor nuked. It was the first time that the motor had ever been above 5000 RPM's and I was at @ 5300 when it let go." - hawks407
Ray, to say the increased RPM (and HP) of the 103 kit cannot be linked to the piston failure is a bit of a stretch. It may or may not have played a factor in the engine's demise. It is a bit of a coincidence the motor runs trouble free for 110 hours and the first time it is taken beyond its intended operating RPM range it breaks a piston. It is common knowledge that turning too many RPM with a cast or hypereutic piston can cause them to break. Do you have pics of the broken piston? Did it pull the wrist pin out of the piston? Did the piston show signs of detonation?