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The Lotus-Ford Twin Cam is a 1557 cc engine developed for the 1962 Lotus Elan and also used in a variety of other vehicles up until the mid 1970s. ==Design== Lotus required a low cost, compact, yet powerful engine for the Elan, as the custom-built all-aluminium Coventry Climax FWE for Elite was very costly. Colin Chapman initially chose to use the overhead valve (OHV) cast iron block Ford 105E inline four used in the Ford Anglia as the basis of this new engine. While the basic engine design was oriented toward performance (being of oversquare design with individual intake and exhaust ports that are not siamesed), 105E was by no means a performance engine. Soon the 109E for Ford Consul Classic became available, and most of the development was carried out on this three bearing 109E block. To achieve the power required, Chapman commissioned Harry Mundy (of BRM V16 fame) to design a dual overhead camshaft (DOHC) conversion. This comprised an aluminium cylinder head and an aluminium front cover and its back plate assembly containing the water pump and the camshaft drive chain. However, the 5 main bearing version for Consul Capri became available in time for production, and the design was converted on this 116E block, crankshaft and 125E Type C conrods. After the initial design was finished, Richard Ansdale, as an outside consultant, provided the detail design and drew the plans needed for production. Steve Sanville, a Lotus employee, headed the production engineering team including Mike Costin, Neil Francis and Bob Dance, which incorporated the port shape modifications suggested by Harry Weslake, who conducted a flow bench analysis on the head. Keith Duckworth had already left Lotus, but was responsible for Special Equipment cam design, as well as the assembly of the first two production-specification engines, one of which powered Lotus 23 on its sensational debut at Nürburgring. Likely reflecting Chapman's obsession (as an engineer, he was known to go to the extreme in lightweight designs) to save weight by using one mechanical part for as many purposes as possible, the water pump used the engine front cover as its housing, making water pump replacement difficult. The intake manifold was cast as an integral part of the cylinder head, making the later heads using Stromberg carburetors not interchangeable with those for Weber or Dell'Orto carburetors. These designs were unique then, and very few have followed suit. Also notable is that the original camshaft was retained as an intermediate shaft driving the DOHC cam sprockets via a front-mounted, single – long – timing chain, having the side-mounted distributor and nearby external oil pump/filter assembly in original locations, requiring few modifications to the mass-produced iron block. Originally, the engine had a bore of 3-3/16" (80.9625 mm) and 72.75mm (2.8642 inches) stroke for a capacity of and produced approximately at 5700rpm. This compares to the original Ford pushrod 116E of about at 4600rpm. After the initial 50 engines were contracted out and assembled by J.A.Prestwich, the specification was changed to a larger 3-1/4" (82.5500 mm) bore, increasing the capacity to . Only 22 of the 1.5 Litre engines made their way into roadgoing "Elan 1500", the rest being used on Lotus 20B, 22, 23, 26R as well as in Elan and Lotus Cortina prototypes and a LHD Ford Anglia mule, which, fit with one of the first prototype engines, had overtaken a fast Jaguar at well over 100 mph in the hands of Jim Clark on his way back from Goodwood to Scotland. The displacement of the new specification allowed an overbore of as permitted by the FIA regulations, while keeping the cubic capacity below the new FIA 1600 cc class limit. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lotus-Ford Twin Cam」の詳細全文を読む スポンサード リンク
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