\u201c<\/em><\/strong>Where a Lotus manufactured part is not essential to meet use a mass produced part from the motor industry\u201d<\/em><\/p>\n Tony Rudd\u2019s \u201cDefinitions and Philosophy of Lotus\u2019s Engineering Policy\u201d 17.4.1975<\/em><\/p>\n Introduction<\/strong><\/p>\n This article is not a technical dissertation on the Lotus Twin Cam engine.Subscribers can find that elsewhere; particularly in Wilkins [see references below].In order to grasp some of the economics of the Twin cam engine its necessary to make reference to the Lotus Elan and the Lotus Cortina.<\/p>\n In this article we debate the importance of:-<\/p>\n The editors consider it helpful in evaluating\u00a0 the Lotus Twin Cam and Chapman\u2019s entrepreneurial sprit to refer to A&R Lotus engine themed articles:-<\/p>\n Figure 1.These item really reinforces the connections that Chapman made and converted to both a mass produced saloon, competition model and income stream<\/p>\n Background and Context<\/strong><\/p>\n By the late 1950\u2019s Colin chapman and his Lotus marque were automobile manufacturers and it\u2019s probable that Chapman saw this as both complementary and a subsidy towards his Motor Racing ambitions.<\/p>\n However in his first significant venture the Elite launched in 1957. We are told by Crombac that it\u2019s probable that Lotus were losing about \u00a3100 on each of these. A rethink was required, lessons needed to be learnt and significantly a replacement needed to be easier and cheaper to make and to be sold at a profit at a more acceptable price.<\/p>\n Therefore through 1962 Colin and his colleagues particularly Ron Hickman set about what would become the Elan [launched at Earls Court Motor show, 1962].They identified that a small open sports car [the most traditional type sold in volume] and the American market particularly California would be shape the product\/ concept. If the car was to be small, compact, economical to own and run yet with distinctive Lotus performance a careful package would have to be sourced.<\/p>\n Taylor reinforcing this point explains in the context of the Elan:-<\/p>\n \u201cWhatever can be said of the Elite it had been a salutary experience for Lotus. The monocoque body shell was an ambitious move and the Elite lost Lotus a lot of money. There was a better way, and Chapman saw it in the backbone chassis which would become a Lotus hallmark for years to come. It made its debut in the Elite\u2019s replacement, the Elan, a model which was crucial to Lotus\u2019 future.<\/p>\n Initially the idea had been to create\u00a0 a low-cost\u00a0 updated replacement for the Seven \u00a0, but by 1961 it was clear that in order for Lotus to remain profitable , it was the Elite which had to be supplanted \u2026\u2026\u2026\u2026overall its design had less of the Elite\u2019s uncompromised feel and far more regard for production viability and costings\u201d<\/p>\n Crombac explains the critical factor:-<\/p>\n \u201cthe crux of the matter was , of course the engine, and bearing in mind the success\u00a0 he had achieved in the early days , using what was basically mass produced engines, Colin decided he should look to see what some of the big manufacturers were able to offer\u2026\u2026\u2026. Ford had also recently introduced a new short stroke 1000cc engine , which on paper seemed attractive but was really not sufficiently powerful .so Colin took the decision to build a special twin cam overhead camshaft cylinder head to fit the block of this engine , entrusting the actual design to Harry Munday\u2026\u2026..chapman discovered that Ford were about to introduce a brand new 1,500 cc engine , with a crankshaft running in five main bearings and therefore very much stronger .it was just what he wanted and the new cylinder head was quickly adapted to suit it\u201d<\/p>\n Crombac also notes the very significant coincidence:-<\/p>\n \u201cColin went to see Wally Hayes to talk about the twin cam engine project, at just about the time he had been charged with the task of strengthening the image of the Ford range, especially with the object of attracting a younger market. The parent company, Ford of America, had been pursuing, that policy and were just about to launch their world \u2013wide \u201cTotal Performance\u201d programme , in which Lotus would soon play an important part.<\/p>\n When Wally Hayes heard about the twin-cam 1,500 cc engine project , he immediately conceived the idea of putting this into the Ford Cortina saloon car which was proving so successful in the family car market\u2026\u2026\u2026\u2026\u201d<\/p>\n Taylor develops the concept details:-<\/p>\n \u201cpreliminary work was on the 3 bearing 109 E block until the Ford 116 E , 5 bearing block became available\u2026\u2026\u2026\u2026the head , pushrods, timing cover and water pump of the original ohv engine were discarded and then Lotus fitted its own aluminium DOHC head\u2026\u2026..however the 100bhp [ i.e. 1499cc] was quickly superseded by the definitive 1558 cc 15 bhp version \u2026\u2026\u2026.<\/p>\n Initially launched \u2026at the 1962 Earls Court Motor show , the price was \u00a31495 fully built or \u00a31095 in kit form\u2026\u2026\u2026..the Elan attracted over 2000 customers in its first three years and its success almost certainly saved lotus from early demise\u201d\u201d<\/p>\n Complementary to the Elan and sharing the Twin Cam engine was the Ford Lotus Cortina.<\/p>\n Taylor places the Cortina in context when he explains it was:-<\/p>\n \u201cthe forerunner of all this success was the true homologation specials, the Lotus Cortina\u2026\u2026.the initial plan called for Lotus to assemble 1000 cars so that it could be homologated for Group 2 racing\u2026\u2026the right power plant had already been devised in the form of Harry Munday\u2019s twin cam head on the unburstable Ford 1500 Kent bottom end\u2026\u2026\u2026production started in February 1963, the basic price being \u00a3910.\u201d [Note significance that purchase tax was \u00a3190-2s-11d making at total of \u00a31,100-2s-11d]<\/p>\n Taylor also suggests that 2894 models were produced 1963-1966 and that an Mk.II was built by Ford c 1967 and that an estimated 4032 were built.<\/p>\n \u201cas for the MK.1 not only was it a resounding success on the tracks , providing Ford with the high profile sporting image which it sought so badly but it also gave Lotus greater financial stability\u201d<\/p>\n Cam Profile<\/strong><\/p>\n Engine design was not Chapman\u2019s forte but he recognized superior \/specialist abilities. He motivated, recruited or used consultants when appropriate. It\u2019s important to appreciate the following engineers made significant contributions to the reaalisation of the Twin Cam. This proceeded through stages of outline specification\/concept to working drawings, patterns, machining, ancillaries and assembly.<\/p>\n Haskell records the significant contributions of:-<\/p>\n \u201cColin Chapman\u2019s contribution to the design of engines and gearboxes was relatively small as a designer, his contribution as an entrepreneur however was much greater \u2026\u2026\u2026\u2026 Chapmans influence inn these early stages was very great and he was as usual a powerful motivating force\u201d<\/p>\n Design [for brevity from the net]<\/strong><\/p>\n 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.<\/p>\n Colin Chapman initially chose to use the overhead valve (OHV) cast iron block 997\u00a0cc (60.8\u00a0cu\u00a0in) 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 over square design with individual intake and exhaust ports that are not siamesed), 105E was by no means a performance engine. Soon the 1,339\u00a0cc (81.7\u00a0cu\u00a0in) 109E for Ford Consul Classic became available, and most of the development was carried out on this three bearing 109E block.<\/p>\n 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\u00a0cc (91.4\u00a0cu\u00a0in) 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.<\/p>\n 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 N\u00fcrburgring.[1]<\/sup><\/p>\n 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.<\/p>\n Also notable is that the original camshaft was retained as an intermediate shaft driving the DOHC cam sprockets via a front-mounted, single \u2013 long \u2013 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.<\/p>\n Originally, the engine had a bore of 3-3\/16″ (80.9625\u00a0mm) and 72.75mm (2.8642\u00a0inches) stroke for a capacity of 1,498\u00a0cc (91.4\u00a0cu\u00a0in) and produced approximately 100\u00a0bhp (75\u00a0kW) at 5700rpm. This compares to the original Ford pushrod 116E of about 60\u00a0bhp (45\u00a0kW) at 4600rpm.<\/p>\n 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\u00a0mm) bore, increasing the capacity to 1,557\u00a0cc (95.0\u00a0cu\u00a0in). Only 22 of the 1.5 Litre engines made their way into road going “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\u00a0mph in the hands of Jim Clark on his way back from Goodwood to Scotland.[2]<\/sup> The 1,557\u00a0cc (95.0\u00a0cu\u00a0in) displacement of the new specification allowed an overbore of 0.040\u00a0in (1.0\u00a0mm) as permitted by the FIA regulations, while keeping the cubic capacity below the new FIA 1600 cc class limit.<\/p>\n Figure 2.Editor’s photograph of Lotus Twin cam in Lotus Ford Cortina<\/p>\n Figure 3.Editor\u2019s sketch of Twin Cam installed in Seven. Note some plumbing and wiring left out for clarity and to simplify drawing<\/p>\n Form and Function<\/strong><\/p>\n \u201cMotor\u201d Sports Car Road Tests featured both the Ford Lotus Cortina and the Lotus Elan in their 1965 edition.<\/p>\n They observed about the performance and economy of the Ford Lotus Cortina that:-<\/p>\n \u201cLotus modifications for the Ford Cortina 1500 engine are extensive ; a small increase in bore raises the capacity to 1,558 cc and a twin\u00a0 camshaft cylinder head with two double choke Weber carburetors increases power output by more than 75% and torque by 33% in the middle speed range.it is this tremendous surge of mid-range acceleration which makes the performance so vivid\u2026\u2026..[they include a photograph of the engine bay with the caption twin ohc head two double choke <\/em>Weber\u2019s , four branch exhaust system and vacumn servo brake unit completely obscure the Ford origin of the engine\u2026.<\/em><\/p>\n And on the Elan they comment:-<\/p>\n \u201cThe performance is little short of phenomenal, not only through the gears and for tractability in the high gears, but for its complete lack of temperament \u2026..this Lotus conversion of the ford five bearing engine is now well known , but the sight of the twin camboxes with their crackle-blue finish is still an exciting hint of power\u2026\u2026\u2026\u201d<\/p>\n In order to partly understand the economic dimension of the TwinCam subscribers might like to note that \u201cMotor\u201d in 1965 recorded a price of an assembled car as \u00a31,436.<\/p>\n\n
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