The marks on different year 235/261 are in different locations and there might be types of symbols.
I guess, at a minimum, they would be at least three marks (unless some of the marks in certain years are in the same place on the fluwheel).
1. UDC or TDC - Upper/Top Dead Center
2. The "tune-up" timing mark, which might be different degrees before or after or on TDC/UDC (depending on the engine and year)
3. Valve timing mark (
a triangle, as described here in step 4)
I think I recall reading that different kinds of marks might have been used in different years.
The value/meaning of those marks on the flywheel can get even more confusing when a flywheel from a different year/engine is put on your engine.
