The reconditioned exchange Lucas M418G starter motor provides a direct original-specification replacement for the MGC. The C-series six-cylinder engine, with its seven main bearing crankshaft and substantial rotating mass, demands more from the starter motor than the MGB's lighter four-cylinder unit, the starter must crank a heavier engine through more compression strokes per revolution, and any weakness in the starter is immediately apparent as slow or laboured cranking. For improved starting, the Hi-Torque starter motor delivers 200% more torque while using 50% less current, cranking the engine faster with less drain on the battery. The Hi-Torque unit is compact, lightweight, and fitted with a direct-acting solenoid that eliminates the separate solenoid relay used with the standard Lucas motor.
Mounting and Specification
Both starter types use two mounting fasteners, one long bolt and one short screw, with spring washers, though the short screw length differs between manual and automatic gearbox installations owing to the different bell housing thickness. The starter motor engages with the ring gear on the flywheel (manual gearbox) or drive plate (automatic gearbox) via a Bendix or pre-engaged drive mechanism. The starter motor was revised from engine numbers 29G/624 and 29GA/127, with a new type of solenoid and associated changes, when ordering a replacement, the engine number should be confirmed to ensure the correct specification is supplied.
Starter Motor Components
A brush kit is available for rebuilding the original M418G, worn brushes are the most common cause of a starter motor that cranks slowly despite a fully charged battery, as the reduced contact area increases electrical resistance and reduces the motor's torque. The solenoid assembly is available separately for the standard unit (not applicable to the Hi-Torque motor, which has an integrated solenoid). A clicking solenoid that fails to engage the starter indicates either a faulty solenoid, a weak battery, or corroded connections at the battery terminals or earth strap.