Definitely a clearance problem, but also every owner tends to start and run their engines differently........Being a mechanic, I have never revved an engine straight away from a cold start........but I have watched many who happily do, including folk at the race track, fire their engines and rev the guts out straight away. The outer cam bush definitely shrinks in size when the cam pinion gear is pressed on....... I get them honed to size at the engine shop.......folk might say this is incorrect, well you can do far more damage with a reamer if your not careful. Very easy to press a cam pinion on crooked as well, it will happily broach its way home.......... Any press fit item, linish/polish a slight taper on the end of the cam, start the assembly a small amount, slide the cam assembly onto another spindle mounted in the lathe, then spin the cam and see how true the pinion is.......realign as necessary, and then press it on further.........Remember to measure twice and cut once.
