The cylinder was filled with water from the intake swap or a gasket leak. When they tried to start the engine, the piston went up and slammed against the water. Water can not be compressed but the other 7 cylinders and starter trying to start the engine slammed the piston into the water with enough force to break the rod. The rod broke instead of bending because it is CAST iron. Cast iron is brittle and will not bend as a forged piece might. After the rod broke the remaining stub of rod attached to the crank started slapping around inside the block and cylinder, breaking pieces of the block out and destroying everything that it could reach.
Some are saying it doesn't make sense for the rod to break at low rpms, but the combination of momentom from the other moving parts, the other cylinders firing and starter was obviously enough when the piston suddenly came to a stop against the water. I'm guessing there was just barely enough water to make it hydrolock, so the piston was high in the cylinder and the crank had excellent mechanical leverage push the rod.
The cylinder was filled with water from the intake swap or a gasket leak. When they tried to start the engine, the piston went up and slammed against the water. Water can not be compressed but the other 7 cylinders and starter trying to start the engine slammed the piston into the water with enough force to break the rod. The rod broke instead of bending because it is CAST iron. Cast iron is brittle and will not bend as a forged piece might. After the rod broke the remaining stub of rod attached to the crank started slapping around inside the block and cylinder, breaking pieces of the block out and destroying everything that it could reach.
Some are saying it doesn't make sense for the rod to break at low rpms, but the combination of momentom from the other moving parts, the other cylinders firing and starter was obviously enough when the piston suddenly came to a stop against the water. I'm guessing there was just barely enough water to make it hydrolock, so the piston was high in the cylinder and the crank had excellent mechanical leverage push the rod.
You are exactly right except the rod part. They are not cast iron. They are powdered metal. A cast iron part is made by pouring or injecting molten iron into a mold. A powdered metal part is made by putting powdered metal (think sand) into a mold then pressing it with an ungodly amount of pressure. I don't know how much cast iron rods would weight, but they would be stronger than the powdered ones.
i couldnt see a stock npi engine just totally pop due to being hydrolocked... just couldnt happen if it was cranked and then let idle... probably more likely to just seize up or bend a rod... unless there is more to the story when they cranked it...