The timing is done with the vaccuum advance disconnected, one way to check the harmonic ballancer to see if it has slipped is to remove the #1 spark plug and insert a dull screw driver down the hole to touch the top of the piston, then place a mark on the balancer at the pointer, then rotate the crankshift past BDC back up so the screwdriver is at the same spot it was before, place another mark, now take the difference between the two markes should be at the TDC if the balancer has not moved.
