Help finding tapping noise.

[85burb]

It is not a ls swap but it is a ls problem. It is a 4.8 in a 07 chevy. It sounds like it has a bad lifter. Like when the roller fails. Well any ways i pulled heads and came and lifters out and everything looks great. The only thing i seen is there is a interesting patteren of the base circle of the cam. Any ideas? Noise comes and goes. It can run a while without it and then it has it at start up and all the time later. Motor has over 272xxx on it. Has almost 40 psi oil pressure hot. I was for sure it was a lifter issue from the noise. I really need help on this. It is a shop truck and me and a guy that worked at chevy were sure it was a lifter. So i ordered all the stuff to do a cam and lifter job. Over a 1000 bucks. My boss is not mad but i feel like a idiot. Thanks!

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