no you missed the entire point, the rusting resulted from sealing of the vents, not allowing the moisture to escape. The end with the breather cap was fine, the other end was the end with the rust. Just the last 3 or 4 inches. If you have no way for the moisture to get out it doesn't matter if there is oil or not, it will still rust. Which is why the military, (at least the navy) went to vapor space inhibitor oils in the large sumps which mostly prevented rusting of the tops of oil tanks. not completely, but it did make a considerable difference. And they did rust, large sheets of it. If I were to use a steel valve cover again, I would seal up the vents and construct some sort of PCV system.
