Description

Vacuum Advance Unit for the ignition distributor on V8 EFI petrol engines, for distributors fitted with a three-pin amplifier module.

The vacuum capsule mounts on the side of the distributor body and connects by small-bore hose to a ported vacuum source on the induction system. Under part throttle and light load the diaphragm is drawn in against its spring and rotates the distributor base plate carrying the pickup, advancing ignition timing ahead of the mechanical centrifugal advance curve. This improves combustion efficiency and part-load fuel consumption.

Note: distributors fitted with a two-pin amplifier module take a different vacuum capsule. Check the module before ordering.

A ruptured diaphragm will not hold vacuum, leaving the engine running on centrifugal advance alone: flat part-throttle response and heavy fuel consumption.