I should warn you that a lot of mechanics will tell you this is normal. My friends teg does the same thing. We've adjusted the valves, and it still does it. He took it to one place, and they told him it was the bearing in the distributor. He replaced it, and it still does it. I still think it's something in the valve train, but other than the noise he's had no problems. He runs the hell out of it too! If he can't blow that motor I don't see how anyone can.