This straight-six engine used a one-piece iron block and non-detachable cylinder head with a crankcase made from Elektron magnesium alloy. As with previous models, it was an OHC design, driven by a Bentley patented "three - throw drive" system of triple connecting rods, with aluminium pistons, twin spark ignition via a pair of magnetos and the usual 4 valve heads. Predictably power and torque were impressive and 220 BHP was the quoted output from the factory. The models were advertised as capable of 125 mph depending on coachwork, with a guarantee of at least 105 mph. A new 4 speed gearbox was developed for the model and the prodigious torque meant you could pull away in top from a walking pace with impunity.

The 8 litre was more or less the Vintage Bentley swansong model before the ill-fated 4 litre and subsequent Rolls Royce takeover and reflected a response to customer demand for ever more luxurious and extravagant coachwork and running gear to match. It has been suggested the development cost of this model led to Bentley's demise into receivership and subsequent acquisition by Rolls-Royce.