time suggesting otherwise. Flatplane crankshafts became the norm in V8 racing engine designs from the 1970s on. F Type At the Olympia Motor Show (in 1923) Coventry Climax listed four F-type 4-cylinder water cooled engines. All had 100 mm stroke, and the bores were 59, 63, 66 and 69 mm. The GWK car had featured in Coventry Climax adverts from late 1920 with a Coventry Climax 10.8 hp 4-cylinder engine, the same horsepower rating as the 66 mm bore F type. The engines were available either separate or in unit construction with a three speed gearbox. ET 2 Also displayed at the 1923 Olympia Motor Show was a twin cylinder 2-stroke engine. The bore was 80 mm and the stroke 85 mm. CX The main engine of interest at the 1923 show was the new 6-cylinder CX engine. This had 61 mm bore and 100 mm stroke, and was rated at 13.8 hp. The same six-cylinder engine appeared in the Waverley car at the 1925 Olympia motor show. The engine size had increased to 1990cc (16 hp rating), with overhead valves and Lanchester style vibration damper, it was coupled to a 4-speed Meadows gearbox. OC At first, the OC was made with a capacity of 1122 cc as a straight-four using a bore of 63 mm and stroke of 90 mm with overhead inlet and side exhaust valves, producing . It was introduced in the early 1930s and also built under licence by Triumph. MC The OC engine had morphed into the MC engine by 1933. It looked virtually identical, but there were internal differences. It was still 1122 cc, I.O.E., and four cylinders inline, but for example, the camshaft was different, as were the cam followers. The timing marks on the flywheel are now observed from the top of the engine rather than the underside (OC engine). Carburation was variable, from the side draught Solex, via the down draught SU, to the progressive choke down draught and larger side draught SU system on Triumph engines. Water-cooled by thermosyphon with no water pump or fan. JM A six-cylinder version of the MC engine, the JM, was made with a capacity of 1476 cc developing . The JMC version had its capacity increased to 1640 cc by increasing the bore to 63 mm and produced . It was different from the 4 cylinder engine in that it had both a water