Vacuum Spark Advance Mechanism

The vacuum advance diaphragm assembly also changes the armature to stator relationship to give spark advance. The stator assembly position is changed by means of vacuum being applied to the diaphragm assembly. Vacuum applied to the diaphragm assembly causes the diaphragm and attached diaphragm rod to move, compressing the advance spring, which controls the rate of advance. The movement of the diaphragm rod, which is attached to the stator assembly, makes the the stator assembly move with respect to the reluctor (armature). This changes the initial reluctor to stator relationship set during initial timing, causing spark advance. The stator assembly is mounted on the lower plate assembly which with the diaphragm assembly, is attached to the distributor base.