Oh yeah, what the head does...

Main parts in the head: Camshafts, valves, valve springs, valve retainers, spark plugs...

Air is pulled into the motor via the intake manifold. I will explain what happens in one cylinder... As the piston (in the block) pull down, your camshafts open up valves that allow air to come in (intake side). When the piston reaches the bottom of its stroke, the camshaft shuts these valves. Now your cylinder is full of air, and is completely sealed (because the valves are all shut. There are two sides for the valves. Intake and exhaust) The piston then rises and compresses the air and fuel mixture into a pretty small area. When that reaches the top of its stroke, and maximum compression, the spark plug ignites the fuel and air, shooting the piston downward. After the piston reaches the bottom again, and starts to come up, the camshaft opens up more valves (exhaust side) to let the exhaust leave the motor. The exhaust gasses pass through ports in the head, through your exhaust manifold (or header) through some piping, and them out your muffler.

The main role of the head in all this is to open and close the valves, controlling when air is let in and out of the cylinders.


This will do a great job explaining...
http://www.howstuffworks.com/engine.htm