I had put out a previous thread on valve clatter and Techron. It turns out that the valves all needed adjustment pretty badly but what mostly caused the clattering (and here I'm a bit fuzzy) is that sludge had developed around the rocker arms and had prevented the oil from being distributed there and/or being recirculated. The indie shop adjusted all the valves, put in a new valve cover gasket and plug and added some heavy duty oil cleaner. He told me to come back after 1000 miles and they'd change the oil. The noise is down about 50% after 50 miles on the road. In researching my Bentley Manual (p.27, section 4.4) I see that the rocker arm shaft has little holes (oil bores). I think they were trying to tell me that these holes got plugged up with sludge and interfered with the oil flow to the rocker arms. Does that make sense?