Under the valve cover you have an oil line running along the cam.. it is squirting oil onto the cam lobes... so in all that air space under the valve cover you have oil being flung about..
In the old days valve covers had ' breathers' on them which was just an opening to the air but with something like brass wool in it... which would accumulate much of the oil and let it drip back into the engine...
Then Clean Air happened and they started taking those fumes and re burning them ... so this tube just goes to the air filter so those oil laden fumes can be sucked back through the engine and exhausted at the tailpipe...
You need to fix that junction between the rubber line and the valve cover.
It does not look to be original... looks to have a hose clamp on it... I think originals are available..
Also renew your gasket on your oil filler hole cover... and when you open that be sure to never turn it upside down... as oil will run into the top and then onto the valve cover when you put it back on...