To advance timing, you rotate the pump counterclockwise as viewed from the front. To retard, move it clockwise. 1 or 2 degrees is equal to about 1/32" It is VERY sensitive. If your "playing" with your timing because you don't have a meter, do yourself a favor and mark it's current position with a center punch. Put the tip between the pump and the housing. This will make a 1/2 circle on each piece, and you can always set it back to where it was. Works much better than a scribed line.