The outer ring of the stock Pontiac damper is marked for top dead center (TDC) only. This makes total timing adjustment an impossible process unless you own a dial-back timing light. A popular modification is to add one or more marks that represent other timing points. Indexing is easily accomplished by measuring the circumference, dividing it by 360 degrees, and multiplying by the desired timing number. Simply scribe another mark that distance from the TDC mark in a clockwise manner. I routinely label mine for easy visual identification.