[edredas]

I'm not sure what the mark I'm pointing to was used for, but it is not useful and isn't on later flywheels. As mentioned it cannot be seen in the OT window and is around the 8 O'clock position if you're facing the flywheel, so its hidden up in the bell housing when the OT mark is lined up. If you need help finding the OT mark you can stick a dowel in the #1 spark plug hole... but finding the exact spot can be tricky since one tooth the other way and the OT mark is out of the window... so what I do is use a dial indicator and when the piston is precisely at the top that is where you will find the OT mark in the window! I hope that helps!