Following full-competition 100S, Austin Healey offered a upgraded road-car known as the 100M.
The package mainly consisted of engine modifications which raised power from 90 to 110 bhp and exceeded the performance of the later six-cylinder models.
To achieve this modest power increase a high-lift camshaft was fitted, along with larger carburetors, higher-compression pistons,
a free-flow intake manifold, a special distributor and a cold air box.
Other upgrades included larger anti-roll bars, while the louvered bonnet was retained by a Le Mans-specification leather strap.
When production ended on July 16, 1956, just 640 examples of the 100M were built. These are distinct from the Le Mans kit that was available to upgrade cars at the dealer or elsewhere.