1998 xj 140xxx miles, bought with 70xxx miles, always changed oil and filter at or under 3000 miles, air filter changed every 6. Yesterday I took a gander with a flashlight down in the valve cover through the oil fill hole and there was this huge clump of oil/greese. I'm talking probably the size of a tenis ball. I cleaned it out with a shop vac and small hose the best i could plus scraped around with a screw driver and sucked some more. This has me worried that the entire head is filled with this crap. ANyone had the same problem? Thinking about taking the valve cover off and giviing the head a good cleaning. What's you thoughts on this? Motor runs like a champ, doesn't smoke, use oil or knock. Oil doesn't turn dark quick like a diesel or nothing after oil changes. I'm pissed. maybe the original owner before me didn't change the oil frequently enough.????