I have a 340. The manual says 2 1/2 degrees advance with the vacuum hose off. I have a new adjustable vacuum distributor and right now its showing about 36 degrees advance when I put the vacuum hose back on. Does anyone know how far advanced I should adjust it to?

 

I think you'll find the link below useful for vacuum advance tuning.
How To Limit and Adjust Chrysler Vacuum Advance Cans

The 3/32 hex inside the nipple does not limit timing, it just controls when it starts coming in (on an OE can anyway).
Some vacuum cans will have the degrees of advance stamped on the arm. This is distributor degrees. Multiply that number by two for crank degrees.

I just recently dealt with this issue. OE Aftermarket cans will never be right . For example, only two cans are offered by Standard for my application VC186 and VC189. The first puts in 22° (Stamped R11) and the second puts in 17° (Stamped R8.5). I had the former so I used a machine screw to limit mine back as 22° VA was too much for my engine.

 

Connecting your vacuum advance canister to manifold vs ported vacuum has becoming a controversial topic online in recent years. Ultimately I think it comes down to personal preference and the setup your working on. Regardless it is important to understand the difference so here is a video on that.

 

The slow method of finding out what your engine wants instead of what you think it wants.

 

Perfect advice

 

Thanks for the info. Mine is aftermarket so I expect some PITA :-)