1937 Rolls-Royce 25/30
The Rolls-Royce 25/30 built between 1936 and 1938 is an updated version of the 20/25 with larger engine to provide more power, as often, over-large bodies had been fitted to the earlier model leading to complaints about its performance.
The in-line 6-cylinder, overhead-valve engine is similar to that used in the 20/25 but increased in capacity to 4,257 cc by increasing the bore from 3.25 inches (82.6 mm) to 3.5 inches (88.9 mm), with the stroke remaining at 4.5 inches (114.3 mm).
The compression ratio is 6:1. 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. The traditional Rolls-Royce radiator with triangular top was used with vertical louvres, the angle of which is controlled thermostatically to control engine cooling.