Page 20 - Demo

Page 20.Alvis Three Litre Shop Manual - T.A. 21 and T.C. 21speed is increased, two spring-loaded weights move outwards under the action of centrifugal forces, causing the cam and rotor arm to advance relative to the driving shaft, so advancing the ignition timing.The optimum ignition timing of the engine depends not only on the engine speed but also upon the engine load. A vacuum-operated diaphragm is connected to the carburettor and is also linked to the plate on which the contact breaker is mounted. As the induction manifold depression is an index of the engine load, any change in load will cause the diaphragm to contract or dilate, producing an angular motion between the cam and its follower so advancing or retarding the ignition to suit the engine load.Adjusting ignition timingLubricating the distributor