helms or chiltons manual shows how to do it. basically, you adjust screws on the end of the rocker arms to take out the clearance between the rocker and the cam lobe.

BTW my teg now has 135,000 and still does it. It hasnt changed. Its a combination of rod rattle on startup (rods plastiguage at .015-.020) and piston slap. when the car warms up the pistons expand and it is pretty quiet.