magnesium cylinder head
The cylinder head is where a great deal of the action for running your engine happens. It contains the combustion chambers where the quick burn of fuel and air that moves the pistons occurs. For this to take place, the cylinder head must be connected to the intake and exhaust manifolds . The intake manifold feeds air into the head through the intake ports, past the intake valves and into the combustion chamber. Once the air and fuel have been combusted, exhaust gasses exit the combustion chamber past the exhaust valves, through the exhaust ports, to the exhaust manifold. The intake and exhaust valves are located inside the cylinder head. These allow fresh fuel and air to enter, and combusted exhaust gasses to exit the chamber, respectively. These must be precisely timed to open and close at the right times to keep the engine running smoothly. This is achieved through a system of parts known as the valvetrain.
The exact parts used in the valvetrain will vary with engine layout, but can contain, in addition to the intake and exhaust valves, rocker arms or a camshaft or two camshafts. Rocker arms push on the valves to open and close them. They in turn are moved by push rods or lifters which respond to the camshaft located in the block. Some engines, instead, have the camshaft located above the valves where it can operate them directly. What parts are present and how exactly they work depends on the configuration of your head and valvetrain.