Blow By

Keep in mind that it's not enough for the PCV system to be apparently intact and giving suction at the end of the valve when you test it with your thumb. It also has to be the correct PCV valve or you'll oil down the air filter (on a '64-up California/'68-up everywhere-else system where the breather's ducted to the air filter) or be driving in a permanent cloud of blowby (on a car without a ducted breather). See here for gory details.