16/4 Specifications

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

Brief History

The 16/4 or Big-4 engine was launched in 1937, as a replacement for the 15/6 (although both survived until the end). It was designed around the same basic principles and features as the succesful 12/4, although it was a litre bigger! The engine initially provided more power than Rileys were used to, but a stiffer chassis and other improvements soon overcame this.
However, despite producing a true 100mph saloon for Riley BEFORE WW2, the engine did not acheive it's full potential for another 20years!

The initial bodies available were the Ever-popular Kestrel and Adelphi, and the new Continental Saloon, unique to the 16/4. A Lynx was also made available shortly after launch (although only one was ever built), as well as the bodyless Chassis, which as far as is known, recieved only one period-body, from Maltby-Redfern. Despite several attempts to fit the Briggs Touring body to the chassis, it is unknown whether any were sold, despite claimed sightings of one in the 1960's.

Following the takeover by Nuffield in 1938, the new 1939 cars shared similar bodies with the 12hp cars, and were initially limited to just a saloon and drophead. The Kestrel was quickly reinstated, due to popular demand.

The engine survived the Nuffield takeover and, with the 12/4, became the mainstay of the postwar RM Series, finally bowing out with the Pathfinder in 1957. In the meantime it had been used by Donald Healey to great effect, in his own cars and had increased in power from 82bhp to 110bhp (or more!).

Engine Development

After the fallout between the brothers over the development of the 12/4 engine, it seems that Percy wasn't even consulted over the new 16/4 engine. Again, it was built on the basic principles of the original 9, so retained a number of Percys innovations. However, nearly a decade later, so much had changed in engine design that the two were almost incomparable. As with the smaller 12/4, the engine was designed with two sizes in mind, but this time there were no shared economies of scale intended, with it being an 'either / or' choice. The smaller version was a 14hp unit, of which a prototype was built and run, but the extra power of the 16hp unit, with minimal extra costs involved, swayed the management in its favour.

Doubtless, had Riley survived as an independent company, the engine would have been steadily developed and improved. Instead, however, it remained in production for two decades, through to 1957 with only minimal updates.


All Big 4 chassis that were productionised were of the same basic dimensions, with a 9'8" Wheelbase and a 4'3" track. The attempts to mate the Big 4 engine with the Briggs Touring Saloon body may have produced some interesting experiments, but it seems unlikely that any were more than one-offs.
The chassis was a development of the latest V8 / 15/6 chassis first seen in 1936, with modified front end to take different suspension layouts. Prototypes with Independent Front Suspension were built, but the productionised chassis retained the axle beam. The V8 chassis was, itself, a development of the wide-track 12/4 chassis, also used for the 6 cylinder cars. Different springs and brake components were also used. The ability to fit different bodies was accommodated by having a variety of body mounting points, to suit all the bodies. This also made it easier to fit special bodies.

The Nuffield 16 chassis was a further development, with modifications to accept different suspension (again), a new petrol tank and a different drive shaft / torque tube arrangement. Curiously, in so doing, the parts commonality between the 16 and 12 model chassis was reduced.

Recognition Features

Whilst there are very few Big 4 engined cars left, they are fairly easy to spot, with the following some of the more obvious features differentiating them from other models: