What would be the best way to 'desludge' a b230F? Upon removing the Valve Cover I discovered bad, really heavy sludge, coke deposits almost plugging the oil passages, covering the head up to the cam lobes, an inch thick in places. Hard to believe the poor thing is running, but, hey, it still purrs like a kitten and I need to save it... Mechanical intervention is tricky since access is tight and I am afraid the junk will fall down the holes and cause worse damage. Any ideas short of removing the head? I know I'll have to drop the pan to clean the oil pump...