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Rolls-Royce B range engines
View on WikipediaThe Rolls-Royce B range was a range of petrol engines first intended to be installed in a car but in 1943 developed into a range to power the British Army's wheeled vehicles.[1]
The Alvis Saladin and Rolls-Royce Phantom IV were fitted with 8-cylinder versions.

Overview
[edit]
Common features
[edit]The B range of engines were all of the inline configuration, with crossflow inlet-over-exhaust cylinder heads and were naturally aspirated. They were heavily rationalized engines, which made use of as many common parts across the range as possible, for example, the 8 cylinder versions used 2 sets of the oil bath air filters, exhaust manifolds and points components of the 4 cylinder, while using the same carburettor as the 6. Pistons, rods, valves, springs, liners, etc. were common across the range, until the introduction of the overbored xx1 series, which still attempted to use as many common components as possible.
The engines were designed to produce relatively high power outputs (for the time), while being extremely reliable and running on low grade "pool" petrol. They were designed to be simple to maintain, with washable oil and fuel filters, mechanical fuel pumps and could all be started via a hand crank.
Models
[edit]The engines were available in 5 main models, which were fitted to small to medium tactical vehicles, up to about 13 tonnes in mass. They were also used in some fixed and mobile plant equipment.
| Model | Configuration | Displacement | Power output | Redline | Bore | Stroke | Produced (approx.) | Applications |
|---|---|---|---|---|---|---|---|---|
| B40 | I4 | 2838 cc | 80 bhp | 3750 rpm | 3.5" | 4.5" | 20,000 | Austin Champ, 10 kW trailer-mounted Generators, Coles crane. |
| B60 | I6 | 4256 cc | 120 bhp | 3750 rpm | 3.5" | 4.5" | 14,500 | Daimler Ferret, Humber 1 Ton, Humber Pig, Humber Hornet |
| B61 | I6 | 4887 cc | 140 bhp | 3750 rpm | 3.75" | 4.5" | ||
| B80 | I8 | 5675 cc | 160 bhp | 3750 rpm | 3.5" | 4.5" | 4,700 | Alvis Saracen, Alvis Saladin, Centurion ARV Winch Motor, Douglas Aircraft Tug |
| B81 | I8 | 6516 cc | 185 bhp | 3750 rpm | 3.75" | 4.5" | 4,000 | Alvis Stalwart, FV430 Series (Mk 1), Alvis Salamander,[2] Schützenpanzer Lang HS.30 |
Leyland 6x6 Recovery vehicle and Leyland 6x6 Gun Tractor
Marks
[edit]The engines were manufactured in 8 marks. For example, the Daimler Ferret was fitted with the B60 Mk 3A in early production and the B60 Mk 6A in the later production examples. The table below details the main differences between the marks, but there were also minor differences, such as changes to pulley configurations and accessories as well. Depending on the fitment of the engine, different accessories may also be installed so, for example, a B80 Mk 6A from an Alvis Saracen is not directly interchangeable with a B80 Mk 6A from an Alvis Saladin, as the Saladin is fitted with a high output 70A generator, and has different mounts for the engine, water piping, accessories and hydraulic system.
| Mark | Threads | Head | Block | Sump | Compression | Min. fuel requirement | Notes |
|---|---|---|---|---|---|---|---|
| Mk 1 | B.S.F. | 80 RON | Prototype only | ||||
| Mk 2 | B.S.F. | Alloy | Iron | Wet | 6.4:1 | 80 RON | |
| Mk 3 | B.S.F. | Alloy | Iron | Dry | 6.4:1 | 80 RON | |
| Mk 4 | B.S.F. | Alloy | Alloy | Wet | 6.4:1 | 80 RON | Prototype only |
| Mk 5 | U.N.F. | Iron | Iron | Wet | 6.4:1 | 80 RON | |
| Mk 6 | U.N.F. | Iron | Iron | Dry | 6.4:1 | 80 RON | |
| Mk 7 | U.N.F. | Iron | Iron | Wet | 7.25:1 | 86 RON | |
| Mk 8 | U.N.F. | Iron | Iron | Dry | 7.25:1 | 86 RON |
History
[edit]The group of engineers at Rolls-Royce's Clan Foundry in Belper Derbyshire led by W. A. Robotham completed development of the Rolls-Royce Meteor engine in 1943 and began work on this rationalised range of petrol engines to power a range of army combat vehicles. Development was completed and manufacture started at Rolls-Royce Crewe in 1947.[3]
B40 engines were required in large numbers for the British Army contract to build 15,000 ¼ton "Champs" over four years (1951-1956) plus spare engines and parts, and a further 400 vehicles for the Australian Army. Rolls-Royce were unable to cope with production at this rate and the Austin Motor Co were granted a licence to produce B40 Mk.5A engines, and also loaned tooling. The majority of Champs produced were fitted with Austin-built engines which are identified by 5-digit serial numbers.
Racing
[edit]In the 1950s, Vanwall raced a highly modified alloy block B40, combined with a cylinder head based on 4 heads from the Norton Manx, in their Vanwall Specials. In race trim, these engines produced 290 bhp at 7,500 RPM when running on alcohol, and after a rule change in late 1957, this was reduced to about 260 bhp on 130 octane aviation fuel. Despite this, the cars were moderately successful, earning the constructor's championship in 1958.
Modern Usage
[edit]Due to the popularity of 1950s and 1960s British Military vehicles with collectors, many Rolls-Royce B range engines are still in use.
- The original MOD specification called for the use of OMD-110 oil, which has a civilian equivalent rating of a straight 30W detergent mineral motor oil[citation needed]. A later specification substituted a 10W30 and some owners use a 20W50 without problems[citation needed]. In any case, owners need to ensure that the oil is compatible with yellow and white metals used in the engine.
- Due to their low compression ratios and hardened valve seats, the B range of engines are suitable for use with unleaded fuel, without modification.[4]
See also
[edit]References
[edit]- ^ Rolls-Royce Motors Holdings Limited. The Times, Monday, May 07, 1973; pg. 23; Issue 58775
- ^ "The Alvis Salamander Fire Crash Tender Chassis". Coventry: Alvis Limited. 24 March 2016. Retrieved 8 August 2021.
- ^ Spencer MBE CEng FIEE, Reginald J. "Rolls-Royce at Clan Foundry, Belper". Rolls-Royce Enthusiasts Club. R.R.E.C Limited. A company registered in England and Wales, No 1154113. Retrieved 25 January 2017.
- ^ Service Bulletin JGH/WAD, Rolls-Royce Motor Cars Limited, Crewe, 1989, p. 1
Bibliography
[edit]- Munro, Bill (2002). Alvis Saracen Family. Ramsbury, England: The Crowood Press Ltd. ISBN 1-86126-537-9.
- Robotham, William Arthur (1970). Silver Ghosts and Silver Dawn. London: Constable.
- Ware, Pat (1994). In National Service. Warehouse Publications. ISBN 0-9525563-0-8.
Rolls-Royce B range engines
View on GrokipediaDesign and Features
Common Characteristics
The Rolls-Royce B range engines share an inline configuration, offered in 4-, 6-, and 8-cylinder variants, featuring robust cast-iron blocks and cylinder heads with overhead inlets and side exhaust valves to optimize airflow and thermal efficiency.[1] These engines employ overhead valves actuated by pushrods from a single camshaft mounted in the block, promoting mechanical simplicity and ease of maintenance in demanding environments.[1] Dry cylinder liners (Bri-chrome) are fitted for enhanced durability, allowing for reliable operation under high-load conditions typical of military applications.[8] A key design principle across the B range is the use of low compression ratios, generally ranging from 6.4:1 to 7.25:1, which enables efficient performance on low-grade fuels such as 80-octane pool petrol without detonation issues.[3] This adaptability stems from the engines' engineering focus on versatility and reliability, with components like pistons, bearings, and scalable crankshaft elements designed for commonality across cylinder counts to streamline production and minimize spare parts inventory.[1] Such shared architecture reduced manufacturing costs while ensuring logistical ease for field repairs.[3] The cooling system is water-based, utilizing centrifugal vane pumps to circulate coolant through the block and heads, paired with rugged radiators engineered for extreme temperatures from -40°C to +50°C and vibration-resistant mounting for military durability.[3] Fuel delivery relies on SU carburetors (single-choke side-draught) for the 4-cylinder B40 and Solex twin-throat down-draught models like the 40 WNHEO-2 for 6- and 8-cylinder variants—to provide precise metering suited to variable operating conditions.[3] Ignition is handled by a coil and distributor system, typically Lucas units operating on 12- or 24-volt supplies, ensuring dependable starting and timing across the range.[3]Models and Specifications
The Rolls-Royce B range engines comprise a family of inline petrol engines designed for versatility in power output, with models differentiated primarily by the number of cylinders and bore diameter. All models share a common stroke of 4.5 inches (114.3 mm) and are naturally aspirated, with compression ratios of 6.4:1 for the B40, B60, and B80, 7.25:1 for the B61, 6.5:1 for the base B81, and 7.25:1 for higher-compression variants of the B81.[3] The B40 is a 4-cylinder engine with a displacement of 2,838 cc (173 cubic inches), delivering 80 bhp at 3,750 rpm and maximum torque of 138 lb-ft at 2,000 rpm; its dry weight is 650 lb (295 kg). The B60, a 6-cylinder model, features 4,256 cc (260 cubic inches) displacement, producing 130 bhp at 3,750 rpm and 209 lb-ft at 2,400 rpm, with a dry weight of 825 lb (374 kg). The B61, a 6-cylinder variant with increased bore, has 4,887 cc (298 cubic inches) displacement, outputting 168 bhp at 4,000 rpm and 268 lb-ft at 2,250 rpm, maintaining the same weight as the B60. The B80 is an 8-cylinder engine of 5,675 cc (346 cubic inches), rated at 195 bhp at 3,750 rpm and 280 lb-ft at 2,250 rpm, weighing 1,000 lb (454 kg). Finally, the B81, an 8-cylinder model with enlarged bore, displaces 6,516 cc (398 cubic inches) and produces 220 bhp at 4,000 rpm (or 235 bhp in 7.25:1 compression form) with 330 lb-ft at 2,300 rpm (or 354 lb-ft at 2,500 rpm) at a dry weight of 1,010 lb (459 kg).[3][4] Fuel consumption for these engines, measured at 3,000 rpm, ranges from 5.5 imperial gallons per hour for the B40 to 14.125 imperial gallons per hour for the B81 Mk.7-8 variant; all models operate on 80-octane fuel, with 86-octane required for higher-compression versions. Operational RPM ranges typically span from idle speeds around 500-600 rpm up to the maximum rated speeds of 3,750-4,000 rpm. Mark-specific adaptations can yield incremental power increases beyond these baseline figures.[3]| Model | Cylinders | Bore (in/mm) | Displacement (cc/cu in) | Power (bhp @ rpm) | Max Torque (lb-ft @ rpm) | Dry Weight (lb/kg) |
|---|---|---|---|---|---|---|
| B40 | 4 | 3.5 / 88.9 | 2,838 / 173 | 80 @ 3,750 | 138 @ 2,000 | 650 / 295 |
| B60 | 6 | 3.5 / 88.9 | 4,256 / 260 | 130 @ 3,750 | 209 @ 2,400 | 825 / 374 |
| B61 | 6 | 3.75 / 95.3 | 4,887 / 298 | 168 @ 4,000 | 268 @ 2,250 | 825 / 374 |
| B80 | 8 | 3.5 / 88.9 | 5,675 / 346 | 195 @ 3,750 | 280 @ 2,250 | 1,000 / 454 |
| B81 | 8 | 3.75 / 95.3 | 6,516 / 398 | 220 @ 4,000 (235 high-comp) | 330 @ 2,300 (354 high-comp @ 2,500) | 1,010 / 459 |
Marks and Variants
The Rolls-Royce B range engines underwent a series of evolutionary marks from Mk 1 to Mk 8, reflecting incremental refinements in materials, lubrication systems, and performance to meet military and industrial demands. These marks primarily addressed issues like weight reduction, reliability in harsh environments, and compatibility with varying fuel qualities, with production spanning from prototypes in 1947 to full-scale output starting around 1950 and continuing into the early 1960s.[4] Early marks focused on adapting pre-war car engine components, while later ones incorporated cast iron construction and unified threading for easier maintenance.[4][3] Key variants within the marks included adaptations for specific applications, such as dry sump configurations for off-road vehicles to prevent oil starvation, and higher compression ratios in later marks to boost power output without major redesigns. For instance, the B60 series saw variants like the Mk 6A, optimized for the Daimler Ferret scout car with a fully waterproofed powerpack delivering 129 bhp at 3,750 rpm.[1] Similarly, the B81 Mk 8 featured enhancements for higher torque in armored vehicles like the Alvis Saracen. Power outputs generally increased modestly across marks; the B60 started at around 130 bhp in early configurations and reached up to 150 bhp in higher-compression variants like the B61, while the B81 ranged from 195 bhp to 235 bhp depending on the mark and compression.[3][8] Non-standard variants included civil designations like Mk 50 and Mk 60 for the B60/B81, which used wet sumps and simplified accessories for non-military uses such as fire engines and generators, and supercharged options like the B61SV for specialized high-output needs. These evolutions ensured the B range's longevity, with over 40,000 units produced across models by the early 1960s.[4][8]| Mark | Key Differentiators | Sump Type | Compression Ratio | Typical Power Output (B60/B81 example) | Production Period |
|---|---|---|---|---|---|
| Mk 1 | Prototype using adapted car crankcases; basic design testing | Wet | 6.4:1 | ~130 bhp (B60) | 1947 (prototypes) |
| Mk 2 | Introduction of alloy cylinder head for better heat dissipation; cast iron block | Wet | 6.4:1 | ~130 bhp (B60) | 1948–1949 |
| Mk 3 | Similar to Mk 2 but with dry sump for improved lubrication in rough terrain | Dry | 6.4:1 | ~130 bhp (B60) | 1949–1950 |
| Mk 4 | Experimental all-alloy head and block for weight reduction; wet sump | Wet | 6.4:1 | ~130 bhp (B60) | 1950 (limited) |
| Mk 5 | Standardized UNF threads; cast iron head and block; simplified components for mass production | Wet | 6.4:1–7.25:1 | 130–150 bhp (B60/B61) | 1950–1955 |
| Mk 6 | Dry sump variant of Mk 5; enhanced for military vehicles like Ferret (Mk 6A) | Dry | 6.4:1–7.25:1 | 129–150 bhp (B60 Mk 6A) | 1951–1960 |
| Mk 7 | Higher compression pistons; wet sump (primarily B81); improved efficiency on 86 RON fuel | Wet | 7.25:1 | 175–200 bhp (B81) | 1955–1960 |
| Mk 8 | Dry sump version of Mk 7; aluminum components in some variants for reduced weight; unleaded-compatible valves in later units | Dry | 7.25:1 | 195–235 bhp (B81) | 1956–1962 |