[Bradical]

There’s a third mark on the flywheel, at the bottom that you can see through a notch in the bellhousing, but there could be 47 marks, you are still only aligning two things, the crank and the cam.

The problem you are having is the slack in the belt turning the cam as you tighten the slack out. Skip the cam gear back a tooth and a half and then when you take up the slack the mark will align.