Editing Timing tabs and damper TDC lines SBC

==Overview== 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-1969 damper has the TDC line on the outer ring at the 2:30 o’clock position- or 2º before the keyway centerline- i.e. the line is to the LEFT of the keyway, looking at the front of the damper or engine. The keyway is seen in the ID of the damper nose. *The damper used from 1969 to about 1984 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 by the aftermarket, unless they're adjustable. *A third timing mark was used from (some) 1978 to about 1995, and nearly all 1984-1995. 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 1984-1995 and is a 6-3/4” diameter damper. ==Relocating the damper line== [[File:RELOCATED DAMPER LINE.jpg|thumb|400px|left|Damper with original "12 o'clock" TDC line re marked for a "2 o'clock" timing tab]] In some cases it might be necessary to relocate the TDC damper line, like to use a different tab position so the tab can be seen easier due to the placement of the front accessories. This can also be done simply to use whatever timing cover/tab that is on hand. The photo shows a damper that was originally for a 12 o'clock timing tab- notice where the original TDC line is located. The damper line was relocated by hacksawing a shallow groove into the damper at the correct location to indicate TDC using the new tab. The new line can be easily highlighted with white paint, etc. so it can be identified as the correct line to use when timing the engine. <br style="clear:both"/> ==Checking the timing tab/damper for accuracy== 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. [[Category:Engine]] [[Category:Adjust valves]] [[Category:Firing orders]] [[Category:Good articles]] [[Category:GM]] [[Category:Ignition]]

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