It has been a while since I installed cam bearings. It is possible to have #4 (I think) cam bearing installed improperly or can the bearing shift enough to allow oil to only one head? If you can run a wire down the oiling hole then do both sides and try to get an exact measurement to see if one side hits the back of the bearing vice the cam. I would think that if you had a difference that it might be something to look at.
