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I noticed that when rotating the engine, number 1 cylinder is at TDC when the harmonic damper mark is at exactly 12 o clock, but the piston starts to come down when it reaches the 0 degree on my timing tab? Why is that? I replaced the harmonic damper recently and just kept the stock timing tab. The tab is at about 2 o clock.
 

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WFO
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You have a damper that uses a timing tab located at the 12 o'clock position. You can set the engine on TDC and remark the damper w/a line that matches the tab.

The following is from another post I made on this:

There are several different dampers. Both the diameter, thickness and the placement of the line on the outer ring of the damper can differ. So you need to know what 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 want to set the engine on TDC accurately, DETERMINE TDC and MAKE A TIMING TAPE to help you set the total timing w/o needing a dial back timing light.
There have been numerous threads on this. If you do a search I'm sure you'll find some of them.
 

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Rod...from a Chrysler?
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Here's a pic of mine. I opted to use a hacksaw to make a shallow groove in the right place and use the 2 o'clock position.

 
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