Wilf:
Your the one beacon on reason!
Guys; I don't care what the Ford rep said; you don't have to adjust the rockers every 800 mi! the clearance is .024; what is wearing within 10% of that? Answer nothing.
Jeff; the needle bearings wear; about 10 mircrons very 5ooo miles. After a needle bearing or any roller for that matter wears more than one or two thousandths of an inch, it's damaged and running rough and is on the path to failure. Check them every
oil change and you be fine. I never find any that have changed more than .oo1 in - ever. My adjusting margin of error is bigger than that.
Also; right; check um hot and burn the cr*p out of yourself.
Hint check a couple of cylinders hot; set at .024 in; then cool the motor and recheck the same two and see what the clearance is cold. It should be smaller. THEN set them cold and avoid the 3 degree burns. . That was SOP for the old air cooled Porsches; way to dangerous to set hot; so the specific factory instructions was for careful cold setting of .002 and .004. When the motor was hot all that alum expanded and the real valve lash was about .015.
gn