[V8] Sticky Tappets and marbles?

[gbmarc at cox.net]

I've changed the timing belt on my car but never touched the tappets or the heads.
Right now, when I start up from cold, I have this clacking noise, or sometimes it sounds a bit like a couple of marbles are knocking around the front RHS of the engine.
Once the engine gets warm, the sound disappears and the noises seem fairly normal.
Has anyone got some input on what a bad tappet sounds like and does this sound like it?
Then I guess the next question is, how to fix it?  (Or do I wait until the next timing belt change?)
Mark.