Oil in the air cleaner 300D

[Subman]

There is always oil in the air cleaner of my 1980 300D. It dose have 144K on it, but the head was taken off, valve gides replaced and cleaned out (due to oil in the intake from a broken gasget in the vacume pump, but that is a whole other stoy). The original air cleaner has been replace with a new one (old one broke). If this matters it is a California car, the valve case vent goes into the air intake to get rid of the fumes. The head was done 9K ago and the air filter is oily and dirty.
Is this normal?? What can I do ??
I have had a sugueston to rig the vent to a pipe going to the bottom of the motor and venting the oil and gasses onto the ground. I dont like this idea to much because it is bad for the enviroment and I will lose some oil.

Thank You for any suguestions.

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-1999 ML320
-1995 E320
-1994 E420 (lowered 1.5 in useing Eibach)
-1980 300D
-Had 1985 300TD Wagon (for over 10 yrs)
-Had 1993 190E 2.3