Being a 1974 2.3 , the first year for the engine I have to say it's the valve stem seals , and sitting over the years the rubber valve stem seals gets hard and just crumbles, and with the cam on top of it all you have eight hole in the cam squirting oil at 60 psi all inside the valve cover it works its way the combustion chamber, but do not run the engine without the valve cover , years ago a good friend learned a lesson when oil from the cam put some nice oil stripes on the ceiling and himself , priceless 😆