Distributor Help/Identification

[z3beemer]

I'm nearing an attempted start up on my 73 complete restoration.  The 73 was originally a auto with dual points,  I've converted to a manual with roundtop carbs, intake and distributor with single points from a 72. I trying to interpret the timing plate in the distributor.  Attached are two pics, one from the 73FSM the other an actual pic of the indicator on the distributor.   There is not a similar pic in the 72 FSM.  The pic from the 73 shows 3 lines pointing to the indicator. Unfortunately, there are two arrows pointing to the bottom line labeled 4 degrees and 8 degrees.  The center line and the top line have arrows but no labels.  I'm assuming a misprint.  The second picture is the actual indicator on the distributor.  Here are my assumptions, let me know it this sound right:  The R on the left stands for retard, the A on the right stands for Advance.  The center line on the indicator (the longer line) is TDC. Moving towards the A increases advance until maximum advance is achieved when you reach the A. Likewise, moving towards the left increases retard until maximum retard is reached when you reach the R.  I have no idea how many degrees of advance or retard is represented by each increment ( 2 degrees or 5 degrees).  Sooo, are my assumptions correct? If so, how many degrees are represented by each increment? If I'm incorrect, can someone enlighten me?  On a related note, what should the timing be?  I've seen 6 degrees and 17 degrees.  One said it was 6 degrees for USA cars.  I assume that was due to emissions requirements.  Since I do not have to have emission testing and I've removed most all the emission equipment when I converted to roundtops (72 standards), what would be a good timing setting?  As usual, thanks in advance for your assistance.

 

[SteveJ]

The manual is saying the marks are 4º apart.

 

There is one screw that allows you to adjust this indicator relative to the distributor mounting bracket. There is another screw that allows you to adjust the distributor relative to the indicator. When you adjust both, you can get well over 8º advance at idle.

 

Edited April 18, 2023 by SteveJ

[Zed Head]

1 hour ago, z3beemer said:

On a related note, what should the timing be?

I'd check your mechanical advance weights and see what maximum advance will be at high RPM, full throttle.  Then do the math to get about 32 - 34 degrees total.  That's the magic number for best performance for most engines.  Don't forget to double the number stamped on the weights since they are distributor degrees not crankshaft.  e.g. weights stamped 9 will give 18 degrees mechanical.  I've seen 11's.  34 - 22 = 12.

You might even have 12's.  Always a good idea to check the centrifugal mechanism anyway, sometimes things get gummed up or fall apart.

Here's the plots from the 73 FSM.

[siteunseen]

Check out this spreadsheet walter moore put together.

Distributor advance curves.xls