why is my airfilter ful of oil ?

My Dart /6 does the same thing. Replaced the PCV valve and the other valve cover breather cap and it helped. Make sure your good and tuned up and your carb is tuned as well so you have the best vacuum she'll produce. Also adjust your valves if you haven't already done so. That's about all you can do. Just make sure she's running the best she possibly can and keep the oil changed and clean. The basic problem is blow-by from your rings. You can perform a compression test and a leak down test to determine the severity but it just comes with age.