I don't think that sounds like crank bearings. They have a deeper tone, like a five pound sledge hitting a solid piece of metal.

It sounds like your cam is making the noise. Pull the valve cover and check the cam for grooves and check the cam followers for wear. I know you said you adjusted the valves, but if a cam lobe is grooved or a cam follower is dished out you will get this type of noise.

It could be that one of your cam followers is not seated correctly. If one of them looks askew this is likely your problem.

It is also possible for the adjustments of the valve position have worked loose. If an adjusters turns easily then that one needs to be replaced.