Time for a valve adjustment, several K-miles after a head rebuild. I noticed that, with the crank pulley at "P", the exhaust cam lines up with the marks on the front bearing cap. However, the intake cam is behind it (retarded) as much as 3 - 5 crankshaft degrees. This is a 502 series motor, #13655 , but the cams are inscribed "101-06 FO76". First, are these cams from a different motor? And, is the retardation of the intake cam sufficient that I should address it? The motor runs pretty well, but with some persistent fluffing just off idle.