81-inch Rolls-Royce B40 trial

History

In the late 1940s the British Army pursued standardisation on the Rolls-Royce B-series family of military engines, and needed to evaluate alternative light 4x4 designs alongside the vehicle that became the Austin Champ, which used the same Rolls-Royce B40 four-cylinder unit. To give the Land Rover a comparable powerplant, a batch of 33 standard 80-inch Series I vehicles was delivered in 1950 to Hudson Motors Ltd of Chiswick, London, where, under the supervision of Rover's engineers, they were fitted with the Rolls-Royce B40 Mk 2B petrol engine (about 2.8 litres; the Dunsfold Collection quotes 3.0 litres) driving through a four-speed gearbox.

The bigger, taller engine forced extensive alterations: the transfer box, front panel, floor, exhaust and gauges were all modified, the bonnet was raised to clear a larger radiator, and the rear axle was moved back by an inch — which is why the converted vehicles became known as the '81-inch'. Trials carried out at the Fighting Vehicles Research and Development Establishment over the following couple of years found the B40 installation was no improvement on Rover's own engine, and the proposal was dropped; the Army's B40-powered light 4x4 requirement went to the Austin Champ instead.

Of the roughly 34 conversions, only two are known to survive with the Rolls-Royce engine still installed. One, chassis RO61 04618, was sold by Bonhams in September 2014 for £51,750. The other, chassis R06104455 (registration ESU 229), was used as a parade vehicle after the trials, was displayed at Beverley Museum and then the REME Museum from 2006, and is now preserved in the Dunsfold Collection.

Registry record

Manufacturer

Land Rover (Rover Company)

Manufactured

1950 conversions; trials into the early 1950s

Modifier / coachbuilder

Hudson Motors Ltd, Chiswick, London

Engine type

2.8 L Rolls-Royce B40 Mk 2B petrol inline-four (Dunsfold lists 3.0 L)

Production run

~33-34 conversions

Country of origin

United Kingdom

Status

programme abandoned; two survivors known with the B40 engine, one preserved in the Dunsfold Collection

Catalogue data

Record kind

Named model

Model line

Series I

Wheels

4

Base catalogue fields are exported from the Difflocked game. In-game physics values are arcade tuning, not certified historical measurements, and are deliberately not shown as specifications here.

Sources & citations

Researched sources

• 1950 Series I 81" Rolls Royce Engine (chassis R06104455, ESU 229) ↗ — The Dunsfold Collection (accessed 2026-09-10)
• Rare Rolls-Royce Engined 1950 Land Rover 81" Prototype, chassis RO61 04618 (auction lot, sold 13 September 2014) ↗ — Bonhams (accessed 2026-09-10)

Catalogue references

• https://dunsfoldcollection.co.uk/collection/1950-series-i-81/ https://dunsfoldcollection.co.uk/collection/1950-series-i-81/ ↗

Development reference notes

• 81-inch Rolls-Royce B40 trial · HERITAGE-FLEET-REFERENCES.md

  Raised bonnet and radiator; subtly lengthened wheelbase. Reference: https://dunsfoldcollection.co.uk/collection/1950-series-i-81/

• Early Series I 80-inch and VIP B40 — rolls-royce-81 · HERITAGE-FLEET-REFERENCES.md

  The 80-inch Series I is a selectable wheelbase, with corresponding shorter rear body and headlamps behind the wire grille. User references: `LBG.jpeg` and `images (16)gg.jpeg`. Available body configurations are included in the generated reference catalogue and supported by the workshop and model gallery. The VIP B40 inherits this complete early front and chassis, extending rear axle spacing by one inch to 81 inches. `ESU229-1.jpg`, `ESU229-2.jpg` and `b40.jpeg` show the raised painted rear quarter panels, curved transparent upper shields, framed door tops, raised passenger bench, tailgate fittings, step and ESU 229 plates. The top and rear remain open. Geometry uses copied base panels so future Series I front refinements carry through without another duplicate nose.