My 48 216 had a bad condensation problem in the front of the valve cover this past winter. I went to a hotter thermostat (160 - 180), blocked off the vents, added an open PCV system to no avail. I probably had that valve cover off atleast once a month for the entire winter. While I had it off I'd wipe everything down so my valve train looks pretty good.
You need to remove your valve train and clean it up. All that rust and corrosion took more than one winter to accumulate. That crud thats built up on the rockers is going to flake off, circulate in the oil and eventually damage your bearings.
I don't know what the ultimate fix is for topend condensation but an occasional valve cover removal and wipe down is about the only suggestion I can offer in the winter. I have zero condensation problems in the warm seasons....
Good luck
Dave
