Often confused with the Speed 6, the 6½ Litre was Bentley’s first large-displacement, six-cylinder car. The new engine was necessary to bolster the image of Bentley beyond rivals of Rolls-Royce and Mercedes-Benz. Furthermore, the six-cylinder unit ran much smoother than the 6½.
The new engine was very advanced, using aluminum pistons and a unique valvetrain that employed the use of three crankshafts. While complex, this system was much quieter than the outgoing 6½ Litre.
Although intended for luxury, the advanced engine was raced with great success in the Speed 6.
To keep pace with the larger engine, the chassis was upgraded. Larger disc brakes were fitted with finned aluminum drums.
The first 6½ appeared as a bare chassis at the 1925 Olympia Motor Show, but it would take over a year to launch the car. During this period the engine was thorougly tested and bored out to 6,597cc before market launch.
| type | Series Production Car |
| production years | 1926 – 1928 |
| released at | 1925 Olympia Show |
| built at | England |
| engineers | Walter Owen Bentley |
| production | 545 |
| engine | Inline-6 |
| position | Front Longitudinal |
| aspiration | Natural |
| valvetrain | 4 Valves / Cyl |
| fuel feed | Dual SU Carburetors |
| displacement | 6597 cc / 402.6 in³ |
| bore | 100 mm / 3.94 in |
| stroke | 140 mm / 5.51 in |
| compression | 5.1:1 |
| power | 119.3 kw / 160.0 bhp @ 3500 rpm |
| specific output | 24.25 bhp per litre |
| body / frame | Body over Steel Chassis |
| front brakes | Drums w/Servo Assist |
| rear brakes | Drums w/Servo Assist |
| f suspension | Solid Axle w/Semi-Elliptic Leaf Springs |
| r suspension | Live Axle w/Semi-Elliptic Leaf Springs |
| wheelbase | 3568 mm / 140.5 in |
| transmission | 4-Speed Manual |
| top speed | ~148 kph / 92. |
