I always bought into the cam bore alignment problem. did the tricks with an old cam, etc. what got me thinking differently was the last build I did for myself. I put new bearings in and was trying to decide what cam to use (had several on hand). I noticed one cam wouldn't fit and another just slide right in. i'm betting the bearing journals aren't always concentric with the centerline of the camshaft. reason being is the poor fit thing is inconsistent. I don't have a way to measure journal run out but I think it's worth checking if a serious problem arises.