The in-line 6-cylinder, overhead-valve
25/30 hp engine is similar to that used in the 20/25 but increased in capacity to by increasing the bore from to , with the stroke remaining at . The
compression ratio is 6:1. A single proprietary Stromberg downdraught carburettor replaced the Rolls-Royce one, and magneto ignition was no longer fitted, but a standby coil was provided. The four-speed gearbox is mounted in unit with the engine, and a traditional right-hand change used.
Synchromesh is fitted to third and top gears. The riveted chassis has rigid front and rear axles suspended by half-elliptic springs with hydraulic dampers. Braking is on all four wheels assisted by a mechanical servo, famously under licence of
Hispano-Suiza. Separate rear brakes are fitted for the handbrake. The traditional Rolls-Royce radiator with triangular top was used with vertical louvres, the opening angle of which is controlled thermostatically to control engine cooling. ==Bodywork==