The standard MGB starter motor is adequate for a well-maintained engine in good condition, but on a car with higher compression, a rebuilt engine on initial start-up, or one regularly used in cold weather, a hi-torque upgrade makes a noticeable difference to cold starting confidence. The geared reduction principle draws less current from the battery while generating more torque at the ring gear, which also reduces wear on both the starter and the flywheel teeth over time. The geared hi-torque inertia starter suits 3-synchro cars to 1967. The geared hi-torque pre-engaged starter covers 4-synchro cars from 1968 onwards.
For owners where engine bay space is a consideration, particularly on V8 conversions, a slimline pre-engaged unit and a micro pre-engaged unit are available, the micro being the most compact option for tight installations.