Oil pressure comes up through the block, around (one, or more not sure) of the Head bolts, from there the pressure pushes it through the rocker tubes. if you look at each of the rocker tubes there are little holes (like a garden hose) at each of the rocker locations. the pressure pushes it out the holes keeping the rocker arm lubed on the rail.
I forgot how the cam gets lubed though.
but i remember studying it when i rebuilt my engine last fall.
