What do porting, polishing, and headwork mean?
Headwork means modifying the original cylinder head, which is the top part of the engine containing the combustion chambers, valvetrain, and passages where air/fuel mix flows in and exhaust gases flow out. Typically this is done by two seperate processes called ‘porting’ and ‘polishing’. Porting means that the openings at each end of the head are bored out to a larger diameter in order to improve flow. Often they are ‘port matched’ to the intake manifold or exhaust manifold/header, meaning that any offsets or misalignments between the two parts are machined out. Sometimes the valve openings are modified as well. Polishing means that the inside of each passage is polished from a rough cast surface to a smooth finish. This reduces drag as the combustion gases move along the walls and therefor increases the velocity of the air/fuel mixture. This can be done by hand, or by a process called ‘extrude honing’ in which an abrasive paste is pumped through at high pressure. Extrude honing is ver
