Lotus-Ford Twin Cam
| Lotus-Ford Twin Cam | |
|---|---|
 |
|
| Overview | |
| Manufacturer | Lotus Cars |
| Also called | Lotus TwinCam, Cosworth Mk.XIII, Cosworth Mk.XV |
| Production | 1962–1975 |
| Combustion chamber | |
| Configuration | Inline 4 |
| Displacement | 1557.46cc |
| Cylinder bore | 82.55mm (3.25") |
| Piston stroke | 72.75mm (2.864173") |
| Cylinder block alloy | Ford 116E cast iron |
| Cylinder head alloy | Aluminium |
| Valvetrain | DOHC, 2 valves / cyl., chain driven |
| Chronology | |
| Successor | Lotus 907 |
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.
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 997 cc (60.8 cu in) 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 1,339 cc (81.7 cu in) 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 1,498 cc (91.4 cu in) 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.
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