Cylinders act as a guide for the pistons that translate the heat energy of combustion into the mechanical energy necessary to move a vehicle. Piston rings seal the piston to the cylinder to contain combustion gases and also regulate the oil distribution between the piston and cylinder wall. A cylinder head closes in the top of the cylinder forming the combustion chamber which is sealed by a head gasket (head). The head provides space for air and fuel intake valves, exhaust valves, and mounts for spark plugs and fuel injectors.

The distributor is driven by the engine's camshaft and is responsible for timing the spark and distributing it to the correct cylinder. The distributor cap contains a rotor that connects the ignition coil (and its high voltage) to the proper cylinder at the proper point in the stroke cycle.

The purpose of an automobile engine's cooling system is to circulate coolant around the engine so it can absorb and dissipate heat. The water pump pumps coolant through the various components in the system and the radiator cools down coolant after it has heated up after passing through the engine. The thermostat controls the flow of coolant based on engine temperature while the cooling fan draws air through the radiator when the car isn't moving fast enough for unforced air to cool things down on its own.

During the power stroke, just before the piston reaches top dead center, the spark plug fires and ignites the compressed air-fuel mixture. The resulting expansion due to combustion pushes the piston back down the cylinder toward bottom dead center.

A reciprocating engine is an engine whose crankshaft is turned by pistons moving up and down in a cylinder.