1967-289 Vacuum advance problems

I have just replaced the vacuum advance Diaphram unit on my 289. It is the two piece type with hard line attached to the front and running to the Carb.The new diaphram unit came as the housing only, I took the spring along with the plastic stopper and washers out of the old one and used them. I am have adjusted the machanical timing and carb, but when I connect the vacuum line and add throttle, the advance goes off of the scale and the engine begins to miss-fire. It would seem to me the advance should be gradual and stop at a certain point. Does anyone know how this adjustment is done or is it as simple as adding more washer's (Shimms)to the Diaphram to limit the travel?  Thanks  

You are correct. It should be more gradual. You may have the vacuum line connected to the wrong port on your carb. It should be ported vacuum not manifold vacuum.

What kind of carb do you have? Also use a timing light to check to see just how much it advances with the vac advance connected so you know how far off it is.

Also some of the newer repro diaphrams have a small allen nut in the center of the diaphram to adjust tension and travel. Access it through the front of the can where the vac hose connects. It may not have one but worth checking just to be sure.  

It is a Autolight 4100 for 289 with a manual Choke. It only has one port and it is on the left side toward the front corner as you face the carb. The Vacuum diaphram is the old style two piece design that has a large nut that you can gain access into the unit. It appears that the adjustment is the amount of shims you put inside, correct??  

You need to go the section 9 of the FSM to understand how to adjust that spring tension and overall amount of advance correctly. jlg  

Correct on port location and shims. Follow jlg2002 recommendation for adjustment.  

The shims are for the speed of advance, there should also have been a round barrel like clynder with a hole in the side that clynder length controls distance of travel which effects total timing.
There are three parts to timing, check your ford shop manual for the specs on your motor (1) initial timing say 6 degrees btdc, (2) govornor advance at specified rpm say 18 degrees, (3) vacuumn advance at specified rpm say 10 degrees , for a total of 34 degrees.
Every ford motor had a different set up dependent on area car was shipped to and body style and gearing, hope this helps.