Believe it or not it is normal.. whether or not it is your valves or not, i dont know.. I know that on my car it was the hydraulic lifters that making almost like a tapping noise until they are freshly lubricated. This all stopped when i did the head gasket on my car and had them redo the head, havent heard the clicking since.

I do know that during the winter i used much lighter weight oil to increase flow on cold starts and this too quieted the lifters down, that is until i had the head redone..

Are you noticing any difference in performance or how the engine runs,, besides the obvious noise?