12 cylinders in 3 banks of four each, one vertical, two at 60°. Liquid cooled.
Bore: 137.7mm (5½in.); Stroke: 130.175mm (5 1/8in.); Capacity: 23,970ccs (23.9l) 1,320hp; Compression ratio: 10.1 Supercharged (rear-mounted gear-driven); Fuel: 25/75 petrol/benzol with 10.75ccs/gall. tetra-ethyl lead additive.
RH tractor drive through co-axial double reduction gearing of .694:1
Length: 65in. Width: 37in. Height: 34in.
Construction: individual cylinders with steel liners and sheet steel-fabricated water jackets. Single aluminium alloy cylinder head for each bank of cylinders into which the four liners were screwed. Double overhead camshafts for each bank of cylinders, driven via bevel gears and vertical shafts from the crankshaft. Two inlet and two exhaust valves per cylinder mounted vertically in the flat-topped combustion chambers. Aluminium alloy flat-topped pistons.
Napier was a long-established company with a reputation for high quality engineering in specialities ranging from the manufacture of printing machinery for the Bank of England to work for Brunel during the building of the Great Western Railway. The company made early motorcars and then undertook sub-contract work on aeroengines for the government at the start of the First World War. It rejoiced in the dreadful Scottish pun of "Nay Peer" or "unequalled" which was the name given to a machine for printing Hansard.
In 1916 Montague Napier became convinced that he could design an aeroengine superior to those he was building under contract and set about the preliminary design for a 12-cylinder, liquid-cooled 3-bank W engine. By 1919 the new Lion engine had emerged. It was compact, rugged and reliable. It powered many bombers and flying boats in the 20s and 30s and was adapted for use in the land speed record motorcars and water speed record boats of Segrave, Campbell, Scott-Paine and Cobb.
Napier went on to manufacture an impressive series of aeroengines, often of hugely complex design such as the Culverin double acting diesel, the Nomad and after F.B. Halford had joined Napier, the H-shaped Rapier and 24-cylinder Dagger and Sabre. The Sabre ultimately developed to produce 3,000hp in Sabre VIII form. Napier Rapiers powered the Short-Mayo S20 composite seaplane Mercury.
Although many modifications were made over the years, the basic design never really changed; the Napier Lion VIID, of which this superb model is a miniature, was one of the Lion VII series specifically developed for racing and, in particular, for the Schneider Trophy Air Race. In 1927, the Schneider Contest was held in Venice; three British seaplanes were entered - a Gloster IVB and two Supermarine S5s - all powered by Lion VIIB engines. Flight Lieutenant Webster won the race in an S5 at air average of more than 281mph. A Supermarine-Napier S5 also held the world Speed Record over 100 kilometers at 283mph and the highest speed over a straight 3 kilometer course at 320mph. In the 1929 Schneider Trophy race a Gloster VI Golden Arrow, powered by a 1,320hp Lion VIID took part but a Supermarine S6 powered by a Rolls-Royce 'R' engine (1,900hp) was the winner.
On the ground, the 'Railton Mobil Special' world record attempt car, built by Reid Railton for John Cobb, employed two Napier Lion VIID engines; in 1938 Cobb set a record of 350.2mph, raising it to 369.74mph in 1939. After the hostilities of the second World War were over, the car was taken out of storage and in 1947 re-set the record at 394.196mph, making a one-way pass of 403mph, the first engine to achieve 400mph on land.