Factory Pestolite distributor-How to adjust vacuum advance?

I have a single point Prestolite distributor that I converted using the Pertronix 3 conversion kit. I had it tested and it works but I was told that the vacuum advance works too quick and it needs to be adjusted. I thought you used an allen wrench but I found out I was wrong and there are thick washers under the removable vacuum advance nipple and a spring. Can anyone tell me how to adjust the vacuum advance on this distributor?
Maybe I add more washers?
See attached picture
Thank you!

Don't you need less washers?

The washers create the preload on the spring. At idle the vacuum is greatest and works with the diaphragm against the spring. Under acceleration the vacuum drops allowing the spring to over come the diaphragm and move the timing. If you want it to be slower it seems you would need less spring tension.

You may be correct... I honestly don't know. I did an internet search but I couldn't find anything .

The easiest way to check would be if you had a tester.

Need to see if I can find on of those machines.

O.K.
THANK YOU

Thinking more about it.

The rate at which it would change would be proportional to the spring rate. Stiffer spring faster change.

The washers are creating a pre-load so that means the range at which it will operate. More washers equals less range. Less washers equals more range.

Since you want to change the rate (speed) you need to change the spring.

more preload = more resistance = slower curve.

Maybe I should see if I can find the washers/springs and maybe it will have instructions???

More detail on what they were saying. other than converting to the P III, was there another issue? EDIT best tool for dist work is a hand held vac pump. idle it/pump it/see how the adv changes (a dialback makes it easy). its also perfect for checking the dist innards on the bench as you pump up the can (how much in hg the adv starts/ends and plate/arm freedom of movement. This was a Sears unit (I ain't a Sears fan but it is decades old/works fine/is indispensible)