Piston Stroke
The distance a piston travels from its lowest point (bottom dead center) to its highest point (top dead center) inside the cylinder.
Piston stroke is the physical distance a piston travels inside an engine cylinder from Bottom Dead Center (BDC) to Top Dead Center (TDC). This distance is determined by the offset design of the crankshaft throws or crankpins. The stroke length is a primary specification that determines the engine's torque characteristics, power band, and displacement.
Engines with a stroke that is longer than the cylinder bore diameter are called "undersquare" or "long-stroke" engines. They typically produce high torque at low RPM, making them ideal for trucks and heavy hauling. Engines with a stroke shorter than the bore are called "oversquare" or "short-stroke" engines. They have lower piston speeds at high RPM, allowing them to rev higher and produce more peak horsepower, common in sports cars.
Modifying an engine's stroke is achieved by installing a custom crankshaft with a longer throw, along with shorter connecting rods or pistons with a higher wrist pin height—a process known as building a "stroker" engine. If a vehicle has suffered engine damage, incorrect stroke or bent connecting rods will prevent the piston from reaching correct TDC, causing cylinder misfires and low compression.