One of the biggest changes that Austin Healey made to the 100 Series was the use of the 2,639 cc six-cylinder engine from the Austin Westminster. With the introduction of the 117 hp power source, the type name simply changed to 100-6, and the car also got a longer wheelbase and an air intake on the hood. The windshield was no longer foldable and two additional seats became optional.

The Austin Healey 100-6 is known as a BN6. This example with chassis 4581 from 1959 is one of the last ones produced. The option of two extra seats, barely big enough to carry two children, was not ordered at the time. The BN6 reached a top speed of over 160 kilometers per hour in a road test. More than 14,000 of the 100-6 were built in the period 1956-1959. Of these, 90% went to the United States.