1957 Austin-Healey 100-6 BN4 Roadster Chassis Number: BN4L040672 The 100-6 BN4, which was introduced to replace the Austin-Healey 100, was instantly recognizable to the public as an Austin-Healey, but it introduced several compelling improvements. Chief amongst these improvements would be its six-cylinder engine. Additional improvements included two small rear seats being added, a fixed windshield, and a wider radiator grille that was mounted in a slightly lower location compared to its predecessor. Where the 100 was clearly a sports car through and through, the 100-6 was clearly intended with added comfort for longer drives in mind, but it still retained the 100’s sporting character.