What I was getting at, cleaning just the visible crud away isn't the whole problem, the rocker shafts are hollow, or were at one time, if they are full of sludge then it will cause trouble. Just the fact that it "was a mess" tells me the entire rocker assembly is probably junk by now. Loosen a rocker arm or two and slide it over and take a look at the under side of the rocker shaft. Most likely all chewed up with heavy scoring and galling.