A piston is a cylindrical piece of metal that moves up and down inside each cylinder, compressing the air-fuel mixture and capturing the force created by the combustion process. This force is then transferred to the crankshaft, via the connecting rod. Symptoms of a Bad or Failing Piston include engine misfire, excessive oil consumption, knocking or slapping noise from inside engine. The crankshaft, connecting rods and bearings are extremely important in every engine build, because they convert the reciprocating motion of the pistons into rotational torque. The longer the stroke, the greater the leverage effect and the greater the torque output of the engine. Time will come that your engine pistons, rings and bearings will wear out. Always remember, when your engine bearings fail, a replacement should immediately be installed. Be sure to have your engine pistons, rings, crankshaft bearings, and connecting rod bearings replace with our aftermarket replacement parts as soon as it starts to give you trouble.