[Trackrash]

The piston slap theory is something to consider. I had thought of that. Listening to the valve covers, does not seem to be the source.

However, I just went out, started it up and listened again with my scope. I listened on the bottom of the motor even on the cylinders, and those were not making the noise. Not an exhaust leak, I am familiar with those.

The only place I hear it with my scope is at the center of the right side cam chain cover.