Just trying to get a little education to help out a friend with motor problems. He had upgrades done to a big block motor by a builder that does a standard upgrade kit. Website shows dyno sheet and horsepower and torque that this kit is supposed to deliver. Twice this motor has destroyed pistons within hours of being on the water. The builder has told my friend that he ran it on the dyno and all looked good. He is also claiming that the 3 bad pistons are the result of a lean condition. The ECM programing was done by the builder. My question is. If you expect a certain horsepower because you do this same build all of the time. And you run a motor that's that lean on a dyno wouldn't you see lower than expected horsepower? I'm wondering if this motor was ever on a dyno. Also would you guys expect a builder to take a look at the spark plugs after a dyno run?