... but what if RTV was used to seal the head gasket, and some got around the oil feed to the cam bearings? It worked its way into the oil passage, and plugged it, and some got pushed up into the oil tubes, where it could not escape, and thus never made it back to the oil filter.

I know this sounds a bit far-fetched, but can't think of anything else that would explain what you describe.

Note added. I just looked at the flow diagram. The RTV could also have gotten into the main passage from the timing chain area. Was the front cover ever off? Pretty common to use RTV to seal it.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe