I am now adjusting my valves and I always have had to move the rocker arms slightly side to side when using the feeler gauge. Doing this, makes sure the arm is perfectly parallel to the cam lobe. If it is not, I will get a false reading and it will show to be the correct gap when in fact the gap is .002" or more. I am careful not to press the valve down which would increses the gap.
Has anybody else had to do this? I didn't see it in the valve adjustment tour.