12/4 Specifications

as Old as the Industry, as modern as the Hour
Featuring: Brief History; Engine Development; Chassis; Recognition Features.

Brief History

The 12/4 range of Rileys were launched in late 1934 as the Riley 1˝ Litre. The original body options were the familiar trio of Falcon, Kestrel, and Lynx. They were designated as 1˝ Litres rather than 12/4s, the name they have always been more generally known by, in order to distance them from the Riley 12/6 models, which were seen as being slightly more upmarket, but at the same time were being phased out in favour of the newer, 'better' 4-cylinder models.
The range was thoroughly overhauled for 1936 season, with the lynx and Falcon bodies changed slightly, and the Kestrel moving to the new 6-light body. In addition, owing to the popularity of the range, three new models were offered, the Merlin, Adelphi and Sprite The Sprite Engine was also available for many of the sportier models.
In 1937 a further update saw the Falcon move over to the Briggs Body, used by the Merlin the previous year. The Merlin was therefore dropped, and a new model, the 'Continental' Touring Saloon introduced. This was to be short lived, however, disappearing the following year, along with the Falcon. In their place, the Briggs body was redeployed once more to form the new bottom of the range Victor and with a new rear end it also became the Touring Saloon.

Engine Development

The 12/4 engine was first concieved in about 1932, to fill the gap between the 9 and 14/6. Percy Riley was of the opinion that his soon to be launched 12/6 development of the 6 cylinder block would fit the bill, but some of his brothers disagreed, and eventually the design of a new engine fell to some recently appointed engineers. They developed a new 4 cylinder block, the overall design closely mirroring Percys 9 engine, but enlarged and refined to give more power. The result, as launched, was the 12/4 engine which entered production in 1934 for the 1935 season. It had been so designed that it could also be produced as a 10hp, designed to provide a small engine to replace the 9, but internal politics meant that this never happened.
The engine was further refined for 1936 season cars, and updated further over the next two years, albeit some of the 'improvements' being quickly reversed when it was discovered that the positive results experienced on the test bench were not replicated in real life. The engine was one of the two retained by Nuffield for 1939 season cars, and continued in production until late 1955, when it was over 20 years old.


During the life of the 12/4 models, four different chassis were used. Three by Riley and then another new chassis for the Nuffield models. There were also special chassis constructed for some of the sports models.
Narrow Track Chassis - 4' Track; 9'1" WB
Developed from the 12/6 chassis, and used on all the original 1934/5 models bearing the 22T chassis designation, and also used for some of the early 26F/L Falcon and Lynx models in 1935/6.
Merlin Chassis - 4' Track; 8'10" WB
This was a development of the 9 chassis, intended to be 'mass produced' rather than building each chassis individually on jigs. In order to take the slightly heavier 12/4 engine, the chassis had some additional plating on the front members, it was also fitted with the standard 12/4 brakes, in place of the smaller 9 units. Only used on the Merlin and Victor, albeit with some more amendments for the latter.
Wide Track Chassis - 4'3" Track; 9'4" WB
This was the biggest of the chassis used for 12/4 models, and featured all the remaining bodies on it between 1936 and 1938. While it became the standard for the 12/4 models after 1936 it was never mounted with any of the other engine options.
Nuffield Chassis - 4' / 4'3" Track; 9' WB
A development of the Merlin chassis, featuring that models front axle and either a Wide Track or Morris rear axle, resulting in different tracks front and rear. Only ever used for the 1939 models - Saloon and Drophead.

Recognition Features

The new 12/4 range was designed to fit neatly between the four-cylinder Nines and the larger sixes, essentially replacing the 12/6 range. However, in reality the chassis were not much larger than that of the Nine, and the bodies were similar, if not quite exactly identical to the larger sixes. From 1936 onwards, the bodies were actually shared on many models with either the Nines or the sixes and later 16/4s. As such, it is often difficult to identify which is which.
Early cars generally had larger bodies than the nines, and shorter bonnets than the sixes, so it is possible, with a good eye, to identify the different resultant proportions between the three. Later cars were often differentiated from the nines by better trim levels, slightly different radiators and larger headlamps. The Kestrel in particular became easy to identify as it moved up to the 6-light body. However, so did the larger cars.
The sixes are always easy to tell from a 12/4 by the longer bonnet, but this was less noticeable compared to the later 16/4s and indeed the larger 8/90s. However, both of those models lost the louvres from the bonnet sides, in favour of Blue or Silver 'Streak' emblems. It isn't easy, but once you get to know the subtle differences, it becomes easier to identify which is which.