Ignition Distributors

Ignition timing is varied with mechanical advance mechanisms, and with vacuum advance and retard systems, if equipped. Some distributors have two single vacuum units which work in opposite directions for advance or retard modes. Other distributors have one double acting vacuum unit with two vacuum lines for advance and retard operation. All late models use distributors with vacuum retard and mechanical advance only. No vacuum advance is used. Stag models also use a distributor with two point sets which operate in parallel to extend dwell period.