Editing Timing tabs and damper TDC lines SBC

There are several different dampers and timing tabs. Both the diameter, thickness and the placement of the line on the outer ring of the damper can differ, as well as how the timing tab is positioned. So you need to know what damper you have, to know what tab to use.

'''The three most common locations for the timing mark on the damper:'''

The exact years of the type of damper timing marks overlap one another, depending on the exact application.

The pre-'69 damper has the TDC line on the outer ring at the 2:30 o’clock position- or 2º before- (i.e. to the LEFT of the keyway, looking at the front of the engine) the keyway centerline. The keyway is seen in the ID of the damper. 
 
The damper used from '69 to about ‘84 has the TDC line at the 2 o’clock position- or 10º before the keyway. You'll find that aftermarket dampers are the 10º type, as are the bolt-on tabs sold in the aftermarket, unless they're adjustable. 

A third timing mark was used from about 1978 to about 1995. It is at the 12 o’clock position- or 40º before the keyway. This damper uses a timing cover that has the tab welded on at about the 12 o'clock position. Professional Products lists the years for this type damper line as being ‘84-’95 and is a 6-3/4” diameter damper.

If you're unsure, or just want to check the accuracy of the tab and damper mark for TDC, [http://www.crankshaftcoalition.com/wiki/Determining_top_dead_center DETERMINE TDC] and [http://www.crankshaftcoalition.com/wiki/How_to_make_a_timing_tape MAKE A TIMING TAPE] will help you to see for yourself


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