Bentley’s beating heart: the engines

There’s never a dull moment with Bentley’s wild motors

GREAT WAR, GREAT ENGINE

Before the First World War,

WO Bentley developed a lightweight copper/aluminium alloy piston for racing. At the outbreak of war, he took his concept to the military and by 1917 the 150bhp Bentley

Rotary 1 (right) was being produced at Humber’s Coventry factory and was fitted to Sopwith Camels fighting Fokkers. By the end of the war, 5000 of the more powerful 230bhp BR2 had been made. WO considered it his greatest achievement.

Peacetime (but not exactly peaceful) achievements included the first 4.5-litre Bentley, Old Number One, immortalised as a participant in the crash at White House Corner, Le Mans 1927, having previously set the lap record. With four cylinders, four valves per cylinder and twin carburettors, it was a technically advanced, reliable 130bhp engine that won everywhere and powered nearly 700 road cars. It wasn’t powerful enough for Birkin though, who supercharged it to WO’s annoyance.

It was followed by a 6.5-litre overheadcam, four-valves-per-cylinder, straight-six monster that made 180bhp in Speed Six form. It crushed the field at Le Mans in 1929. The L Series 6.2 V8 went into production in the 1959 S2, and survives in today’s Mulsanne. It’s gained nearly 400bhp, but the pushrods and aluminium block remain.

SPOILS OF WAR

Rolls-Royce turned its new plant at Crewe over to aero engine manufacture in 1938; 15,000 Merlin engines were made for the war e ort. Bentley’s 3.0-litre straight six and the Merlin share lineage from the valvetrain WO and Rolls-Royce ‘developed’ from a 1914 Mercedes Grand Prix car impounded in London at the outbreak of WW1.

MULTI NATIONAL MASTERPIECE Conceived in Germany, with two narrowangle V6s and a shared crankshaft, the W12 was more compact than a V12. In 2014 the W12 (left) was passed to Crewe, where today’s excellent 600bhp-plus version was developed.