Most likely the clicks you hear are coming from the rockers. It is correct that the valves move only once each every two cycles and it sounds to me as though you have one valve far outside of adjustment. Once again, remove the valve cover and feel for excessive play. I normally set my rockers by feel going for just a tiny bit of clearance when cold. If you can really wiggle them then they are too loose. Use the instructions and a feeler gauge to be sure you are within tolerances. I shoot for the tight end of the specifications.

Mark