Bentley
4½ Litre Supercharged – Welwyn-built racing chassis (Birkin team)

Why it matters

The Welwyn-built team cars were the racing core of the supercharged 4½ Litre 'Blower' project, pursued by Sir Henry Birkin against W.O. Bentley's own preference for larger engines. Although the Blowers never won a major race, they became the most iconic of the Vintage Bentleys, and Team Car #2 later served as the template for Bentley's continuation series.

How rare is it?

Six separate kinds of rarity – never combined into one number.

Each kind of rarity is rated separately and never combined.

Production

Every figure says what it counts.

Independent counts (e.g. engine and colour) are never combined into a calculated figure. Surviving examples are never presented as original production.

History

Birkin, convinced that supercharging was the way forward, set up his own workshops at Welwyn Garden City in 1929 with the blessing of Woolf Barnato and the financial backing of Dorothy Paget. Amherst Villiers designed the Roots-type supercharger. Five chassis were built at Welwyn purely for racing, separate from the 50 production cars built at Cricklewood for homologation.

The team cars raced from 1929 to 1931. At Le Mans in 1930 Birkin passed Caracciola's Mercedes on the Hunaudières straight before Team Car #2 dropped a valve with four hours to go; the same year Birkin finished second in the French Grand Prix against Grand Prix machinery.

Technical specifications

Engine

Transmission & drivetrain

Chassis, body & dimensions

Performance

“Not yet verified” means no source has been checked for that value yet. Nothing is estimated to fill a gap.

Sources

Each number links to the exact facts it supports.

1. 1
   Bentley Drivers Club – Vintage History Level B

   • 5 chassis built at Welwyn solely for racing

   Accessed 2026-11-11
2. 2
   1929 4½ Litre Supercharged Team Car #2 – UU 5872 Level A Bentley Motors (Heritage Collection)

   • 4,398 cc, four cylinders; Mk IV Roots-type supercharger
   • 4,398 cc, 100 x 140 mm
   • 100 x 140 mm bore and stroke
   • 240 bhp at 4,200 rpm (Team Car #2)
   • 240 bhp at 4,200 rpm
   • single dry-plate clutch, 4-speed D-type gearbox
   • Rear-wheel drive
   • guaranteed to reach 125 mph in racing trim

   Accessed 2026-11-11