I just noticed that you are from the cold country too. I would be willing to make a big bet that the oiler tubes are clogged from sludge causing damage to the rocker arms and camshaft. You will need to remove the oiler tubes, flush them with carb cleaner, remove the sludge from the oiler holes with a suitable tool, etc., on both sides of the engine. Be sure to replace the plastic bits for each camshaft. I had this happen on my wife's Euro 79 450SEL many moons ago but caught it fairly early (lots of metal shavings and some wear marks on the cam). Although not a technically correct and complete repair, I did not replace the camshaft and merely replaced the damaged rocker arms and pads on the valves (2 damaged lobes) and drove the car without incident for another 50K miles or so. It all depends on how much damage there is to the camshaft. Slight ridges may be OK. On a customer's 350 the lobes were so damaged that camshaft replacement was required. Good luck. Mark