Engine

The 1,087 cc four-cylinder engine had hemispherical combustion chambers with the valves inclined at 45 degrees in a crossflow head. To save the expense and complication of overhead camshafts, the valves were operated by two camshafts mounted high in the crankcase through short pushrods and rockers. The engine was mounted in the chassis by a rubber bushed bar that ran through the block with a further mount at the rear of the gearbox. Drive was to the rear wheels through a torque tube and spiral bevel live rear axle mounted on semi elliptic springs.

Initially produced with a cone clutch drive train it quickly evolved to have a plate clutch driving through a Silent Third gearbox, then all helical dog change box to an ENV pre-selecta epicyclic gearbox. The engine gradually became stronger, gaining extra webs and internal oil feed to the rockers. The final iteration in the Merlin series gained a single plunger oil pump, replacing the double plunger, and an oil filter amongst many other updates.

Bodies

At launch in July 1926 two body styles were available, a fabric bodied saloon called the Monaco at £285 and a fabric four-seat tourer for £235. The saloon could reach 60 mph (97 km/h) and give 40 mpg_‑imp (7.1 L/100 km; 33 mpg_‑US). Very quickly a further two bodies were offered, the San Remo, an artillery wheeled basic saloon and a two-seater plus dickie open tourer and there was also the option of steel panelling rather than fabric for the four-seater tourer.

The thirties saw further models introduced, 1933 being particularly busy, with the 2 door Lynx, Kestrel, and Falcon all appearing. With each year customers demands for more refinement saw the cars get heavier and heavier so that by 1934 the Monaco and Kestrel were of all Aluminium coachbuilt construction. The Lynx gained 4 doors and lost the disappearing hood.

The Riley Imp, a sports version, was produced in the years 1934-1935, with a prototype version being displayed at the 1933 Motor Show at Olympia, London.^[1] The Imp gained quite a reputation for its good looks with swept back wings. Light bodied competition versions gained success in the 1934 Ulster Tourist Trophy, thereafter being known as the Riley Ulster Imp.^[2] Kay Petre and Dorothy Champney took 13th place in the 1934 Le Mans race in a standard bodied Riley Imp with competition chassis and drivetrain.^[3]

Revisions

After the car's 1926 launch, Mark 1 production actually started in 1927 at Percy's engine factory, due to some resistance in the main works to the new design. It was such a critically acclaimed success that after fewer than a thousand cars had been produced the works quickly shut down side-valve production and tooled up for the new Nine in early 1928. This switch to the main factory coincided with several modernisations of the Mark 1 - the cone clutch was dropped, the gear lever and handbrake were moved from the right to the centre of the car and a Riley steering box was adopted, thus making the car the Mark II. The Mark III was a gentle update of the II at the end of 1928, evolving stronger wheels and a different arrangement of rods to the rear brakes.

The Mark IV was a thorough re working of the Nine. Heavier Riley-made 6-stud hubs and axles replaced the bought-in five-stud items. A new cable braking system was introduced with larger drums. The range of bodies was further extended in 1929 with the Biarritz saloon which was a de-luxe version of the Monaco. The improved brakes were fitted using the Riley continuous cable system and if the cable stretched it could be adjusted from the driver's seat.

The Plus series saw the fuel tank moved to the rear of the chassis and an Autovac adopted, whilst the Plus Ultra adopted a new chassis that dropped between the axles, lowering the car.

More body variants were added over the next few years and in 1934 a Preselector gearbox was offered for £27 extra. The range was slimmed down in 1935 to the Monaco saloon, Kestrel streamlined saloon and Lynx four-seat tourer as the works started gearing up for production of the new 12 hp model.

Steel bodies

In an attempt to keep costs down Riley entered into an agreement with Briggs Manufacturing to produce a steel (non coach-built) body for a newly designed chassis. This new chassis was introduced in 1936 and incorporated such features as Girling rod operated brakes and a prop shaft final drive for the Nine (though the 12 hp variant retained the torque tube). The Briggs body was named the Merlin and was available alongside the last nine Kestrel variant, also built on the "Merlin" chassis. (This body was also used on the narrow track 12/4 chassis as a Falcon, replacing its coachbuilt body.) The Kestrel 9 was also adapted to suit the new Merlin chassis, unfortunately perhaps, also adopting the heavier looking Merlin wings.

The Briggs body evolved through 1937 with a large boot extension to be called the Touring Saloon and an additional body style was added on the same chassis - the higher specified special series Monaco (a completely new design from the previous car). The final version (and last nine model) was the 1938 Victor also available with 1496 cc engine. The Victor had the engine further forward to increase interior room, with the battery moved to the engine bay and smaller diameter wheels were fitted.

The Riley company was bought by Lord Nuffield in 1938 and Nine production ceased as the company pursued a strict two-engine line up, continued after the war with the RM series.