distributor advance mechanical operation

[hemi68charger]

OK, this is one of my weak links, ignitions....

I was messing with my Chrysler distributor today and using my vacuum pump on the distributor advance while on the bench vise. I notice at about 10 inches of vacuum, the breaker plate moves...... As it should I'm sure. I know also there's an access hole where one can place a very small allen wrench and adjust. Is this adjustment one that causes the breaker plate to move with more or less vacuum? Is 10 about normal for this? I take it testing/experiments can be done with the car all together. Adjust the advance and see its reaction to the movement of the adjuster... What's the typical wrench size for the adjustment?

[A383Wing]

if the vac advance is adjustable, I think it was a 1/8" allen wrench

[Back N Black]

With it screwed all the way clockwise, the adjusting plate is all the way forward so there is very little compression on the vacuum spring.  In other words, you are getting lots of advance even with very little vacuum. Keep turning it counter clockwise, which will decrease the sensitivity to vacuum so that less advance comes in for any given vacuum level.

[Nacho-RT74]

if the vac advance is adjustable, I think it was a 1/8" allen wrench

3/32" as far I recall.

[b5blue]

3mm