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Armstrong Siddeley Sapphire
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Armstrong Siddeley Sapphire and Star Sapphire (1953 - 1959)


An entirely new model, the 3.4 litre Sapphire saloon, was introduced late in 1952 for sale in 1953. The engine was of advanced design having hemispherical combustion chambers and developing 120bhp in the first instance, increasing to 125bhp with early development and to 150bhp with the optional twin carburettors. The twin carburettor Sapphire was capable of a genuine 100mph. The Sapphire was introduced with a choice of preselector and synchromesh gearboxes. It became available in an automatic version (Rolls Royce four speed) with the introduction of the Mark II in 1954.

In 1956, the smaller 234 and 236 Sapphire models were introduced as a replacement for the discontinued 16/18HP cars.  The 234 Sapphire had an advanced 4 cylinder version of the Sapphire engine which developed 120bhp and gave the car outstanding performance characteristics. The 236 Sapphire had a reworked version of the 18HP engine developing 85bhp.  A 4 speed synchromesh gearbox was standard on both models with the option of a Laycock de Normanville overdrive. Many 236 Sapphires were fitted with Manumatic clutches. Sadly, these cars were not popular, due mainly to their unusual (for the time) body styling, and production ceased in 1958.

Star Sapphire

It is ironic that the best and most handsome of all Armstrong-Siddeley saloons was also the last car it ever made. In the UK, the market for large, middle class machines was increasingly dominated by Jaguar, and though the Sapphire and Star Sapphire types had fine engines and attractive styles, they could not compete on price.

This car had a separate chassis frame and would retain the pre-selector type of transmission for which the marque was noted, but there were two other major innovations. One was that Armstrong-Siddeley elected to assemble their own smart new four-door body shells, and the other was that they designed a new six-cylinder engine, with part-spherical combustion chambers and complex valve gear. The Sapphire of 1953, originally with its 125 bhp/3.4-litre six-cylinder engine, could reach more than 90 mph, and went on sale for £1,728, intending to capture sales in the Jaguar Mk VII market sector. Complete with its noble radiator shell and emblem, and elegant four-door styling, it was a fine machine. With the 150 bhp engine which was also available, it could just reach the magic 100 mph mark.

Right from the start, however, the Sapphire had to face formidable competition, not only from Jaguar, but from Alvis and Daimler. Easier availability, lower prices and a bit more performance would all have helped, but Armstrong-Siddeley’s Coventry factory was not capable of mass production, and the Sapphire became rather an exclusive car.

A massive limousine version was soon made available, but it was the much-improved Star Sapphire, built from 1958 to 1960, which was the star of this range. Looking like, but not identical, to the original car, the ‘Star’ had a 165 bhp/ 4-litre version of the engine, Borg Warner automatic transmission, power-assisted steering and front wheel disc brakes, in what was a very appealing package.

The price of this most comprehensively equipped car, unhappily, had shot up to £2,646, which was too costly to sustain high sales, and although it was a nicely-built, well equipped and very capable saloon, demand slowly ebbed away. Rootes, in the meantime, had copied the engine for a new Humber Super Snipe, in return for letting Armstrong-Siddeley build Sunbeam Alpine sports cars.

In 1960 Armstrong-Siddeley decided to concentrate on making aircraft engines, and pulled out of the car business completely. Between 1953 and 1960, 8,568 cars in this family were produced.

1958 Armstrong Siddeley Star Sapphire

Wheelbase 2896 mm 114 in  
Track front 1470 mm 57.9 in  
rear 1460 mm 57.5 in  
Length 4930 mm 194.1 in  
Width 1880 mm 74 in  
Height 1575 mm 62 in  
Ground clearance 216 mm 8.5 in  
Kerb weight 1778 kg 3920 lb  
Fuel capacity 72.7
UK Gal
US Gal
Type S-6
12 valves total
2 valves per cylinder
Bore × stroke 97.00mm × 90.00mm
3.82 in × 3.54 in
Bore/Stroke ratio 1.08
Displacement 3990 cc
(243.485 cu in)
Unitary capacity 665 cc/cylinder
Compression ratio 7.50:1
Fuel system 2 Ze carbs
Aspiration Normal
Max. output
147 PS (145.0 bhp) (108.1 kW)
@4250 rpm
Max. torque
312.0 Nm (230 lbft) (31.8 kgm)
@2000 rpm
Coolant Water
Specific output 36.3 bhp/litre
0.6 bhp/cu in
Specific torque 78.2 Nm/litre
0-50mph (80 km/h) 11.30s
Top speed 160 km/h
Power-to-weight 81.55 bhp/ton
Engine location Front
Engine alignment Longitudinal
Steering rack & pinion PAS
Turning circle 11.60 m
Suspension Front I.W.CS.
Rear LA.SE.
Brakes F/R Di/Di-S
Brake ∅ F/R / mm
Transmission 3A
Drive RWD
Top gear ratio 1.00
Final drive ratio 3.77