CNC, The dowel pins are what keeps the flywheel from moving they are in with a press fit the TAB keeps them in and the bolts from moving, the pins only go through the crank flange part way there is no way this can loosen! The crank will break before anything that is why I use a steel crank, Have never broke a steel crank.
It is impossible to race an engine and not go through harmonics.
Been doing this since the sixty's when this engine was first made, and found out what worked and did not work, this was my fix and it has not let me down.
