The cylinder head bolts onto the top of the cylinder block where it forms the top of the combustion chamber. It carries the valves and, in many cases, the camshafts.
Cylinder head combustion chambers are designed to help improve the swirl or turbulence of the air-fuel mixture, and prevent fuel droplets settling on the surfaces of the combustion chamber or cylinder walls.
Direct-injection diesels inject into the combustion chamber formed in the top of the piston. For indirect injection, the combustion chamber is a separate chamber formed in the head.
Smaller intake and exhaust passages and ports allow more torque at low engine speeds. At high speeds, smaller passages restrict airflow. Larger passages produce greater power at high engine speeds.
Gaskets form a seal by being compressed between stationary parts where liquid or gas could pass. Gaskets around a rotating part would quickly wear out. Oil seals are used to seal these parts.
Gaskets can be made of soft materials such as cork or rubber, or they can be made of soft alloys and metals. Most gaskets are made to be used only once. Oil seals must also be replaced when a component is overhauled.
