It was the last Bristol to use the BMW-derived pushrod straight six engine that had powered all cars built by the company up to that point.

In a stopgap measure for the 406 its torque was improved by a 245 cc increase in capacity because it was clearly unable to give a performance comparable to that of newer engines emerging at the time.

A prototype with a body by Carrosserie Beutler of Thun in Switzerland was exhibited in 1957 in both Paris and London Motor Shows.

[7] The rear suspension of the 406 also did away with the outdated A-bracket of all previous Bristols for a more modern Watt's linkage.

[2] However, the outdated front suspension of previous Bristols was retained and not updated until the following model with its more powerful drivetrain.