Check the lobe lift on the noisy valve with a magnetic base dial indicator and compare it with another lobe. You didn't mention it it's an intake or an exhaust. Compare the lift with another lobe of the same type because there might be a different lift number. Do you have the "cam card" that came with the new cam? My guess is that you've got a lobe going flat because of an incorrect run-in procedure on the new cam.
Jerry

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