Editing Four-stroke engine (section)

==== Intake/exhaust port flow ====
The output power of an engine is dependent on the ability of intake (air–fuel mixture) and exhaust matter to move quickly through valve ports, typically located in the [[cylinder head]]. To increase an engine's output power, irregularities in the intake and exhaust paths, such as casting flaws, can be removed, and, with the aid of an [[air flow bench]], the radii of valve port turns and [[valve seat]] configuration can be modified to reduce resistance. This process is called [[cylinder head porting|porting]], and it can be done by hand or with a [[CNC]] machine.