What I do to all my briggs is to simply count the number of teeth on the ring gear and then divide 360 by that number. This is the degree each tooth is. Now line up the keyway, and using a marker draw a line on the block even with a tooth on the flywheel and mark the tooth as well. Now advance the number of teeth needed to get to your ideal timing. Look at the advance on the keyway, remeber it. Tighten down the nut. Then loosen and recheck. I have seen the flywheel move as it is being tightened even with an impact.
Lester