Pressure in the Valve Cover (16v)

[hombre@elp.rr.com (John Erickson)]

I guess I just don't understand.  The engine compartment in my car was 
completely covered in oil when I bought it because a) the oil filler cap 
was leaking, and b) there was a big hole in the breather tube.   I have 
remedied both problems, but still get a little oil on the filler cap 
(new).  Every car I have ever owned had some way to relieve pressure in the 
crankcase/valve train.  In most cases, it was some sort of PCV system.  The 
16v doesn't have it.  It only has the breather tube connected to a small 
vacuum line and the air box.  Even with this set up, I do not understand 
why there is pressure in the valve cover.  The oil drain holes in the head 
should allow the pressure to be bled back to the crankcase and on to the 
air box.  I'm sure that the pressure buildup in the valve cover is also why 
we have seal failures and oil in the distributor as well.  These appear to 
be fairly common problems so I don't think I've got anything else I need to 
fix.  Can anyone elaborate on this?  Anyone come up with a solution?

John
87 16v
El Paso