Cam Followers of the Lotus Twin Cam Engine
“Where a Lotus manufactured part is not essential to meet use a mass produced part from the motor industry”
Tony Rudd’s “Definitions and Philosophy of Lotus’s Engineering Policy” 17.4.1975
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.
In this article we debate the importance of:-
- Chapman the entrepeneurial facilitator
- The significance of the Twin cam engine
- Its flexibility and fitting within Lotus models and other marques
- Related to above the form and function of the twin cam engine
The editors consider it helpful in evaluating the Lotus Twin Cam and Chapman’s entrepreneurial sprit to refer to A&R Lotus engine themed articles:-
- Lotus –Power Plants
- The Ford Cosworth DFV
- Austin-Austin Powers
- MG-“T” Total
- Ford side valve-A bit on the side
- Cosworth-‘CosI’s Worth It
- A Holbay in the Engine Bay
- Coventry Climax and Lady Godiva-The naked truth
- Ford Lotus Cortina
Figure 1.These item really reinforces the connections that Chapman made and converted to both a mass produced saloon, competition model and income stream
Background and Context
By the late 1950’s Colin chapman and his Lotus marque were automobile manufacturers and it’s probable that Chapman saw this as both complementary and a subsidy towards his Motor Racing ambitions.
However in his first significant venture the Elite launched in 1957. We are told by Crombac that it’s probable that Lotus were losing about £100 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.
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.
Taylor reinforcing this point explains in the context of the Elan:-
“Whatever 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’s replacement, the Elan, a model which was crucial to Lotus’ future.
Initially the idea had been to create a low-cost updated replacement for the Seven , but by 1961 it was clear that in order for Lotus to remain profitable , it was the Elite which had to be supplanted …………overall its design had less of the Elite’s uncompromised feel and far more regard for production viability and costings”
Crombac explains the critical factor:-
“the crux of the matter was , of course the engine, and bearing in mind the success 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………. 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……..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”
Crombac also notes the very significant coincidence:-
“Colin 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 –wide “Total Performance” programme , in which Lotus would soon play an important part.
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…………”
Taylor develops the concept details:-
“preliminary work was on the 3 bearing 109 E block until the Ford 116 E , 5 bearing block became available…………the head , pushrods, timing cover and water pump of the original ohv engine were discarded and then Lotus fitted its own aluminium DOHC head……..however the 100bhp [ i.e. 1499cc] was quickly superseded by the definitive 1558 cc 15 bhp version ……….
Initially launched …at the 1962 Earls Court Motor show , the price was £1495 fully built or £1095 in kit form………..the Elan attracted over 2000 customers in its first three years and its success almost certainly saved lotus from early demise””
Complementary to the Elan and sharing the Twin Cam engine was the Ford Lotus Cortina.
Taylor places the Cortina in context when he explains it was:-
“the forerunner of all this success was the true homologation specials, the Lotus Cortina…….the initial plan called for Lotus to assemble 1000 cars so that it could be homologated for Group 2 racing……the right power plant had already been devised in the form of Harry Munday’s twin cam head on the unburstable Ford 1500 Kent bottom end………production started in February 1963, the basic price being £910.” [Note significance that purchase tax was £190-2s-11d making at total of £1,100-2s-11d]
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.
“as 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”
Engine design was not Chapman’s forte but he recognized superior /specialist abilities. He motivated, recruited or used consultants when appropriate. It’s 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.
Haskell records the significant contributions of:-
- Harry Munday
- Richard Ansdale
- Steve Sanville
“Colin Chapman’s contribution to the design of engines and gearboxes was relatively small as a designer, his contribution as an entrepreneur however was much greater ………… Chapmans influence inn these early stages was very great and he was as usual a powerful motivating force”
Design [for brevity from the net]
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 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 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.
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 1,498 cc (91.4 cu in) and produced approximately 100 bhp (75 kW) at 5700rpm. This compares to the original Ford pushrod 116E of about 60 bhp (45 kW) 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 1,557 cc (95.0 cu in). 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 mph in the hands of Jim Clark on his way back from Goodwood to Scotland. The 1,557 cc (95.0 cu in) displacement of the new specification allowed an overbore of 0.040 in (1.0 mm) as permitted by the FIA regulations, while keeping the cubic capacity below the new FIA 1600 cc class limit.
Figure 2.Editor’s photograph of Lotus Twin cam in Lotus Ford Cortina
Figure 3.Editor’s sketch of Twin Cam installed in Seven. Note some plumbing and wiring left out for clarity and to simplify drawing
Form and Function
“Motor” Sports Car Road Tests featured both the Ford Lotus Cortina and the Lotus Elan in their 1965 edition.
They observed about the performance and economy of the Ford Lotus Cortina that:-
“Lotus modifications for the Ford Cortina 1500 engine are extensive ; a small increase in bore raises the capacity to 1,558 cc and a twin 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……..[they include a photograph of the engine bay with the caption twin ohc head two double choke Weber’s , four branch exhaust system and vacumn servo brake unit completely obscure the Ford origin of the engine….
And on the Elan they comment:-
“The 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 …..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………”
In order to partly understand the economic dimension of the TwinCam subscribers might like to note that “Motor” in 1965 recorded a price of an assembled car as £1,436.
Figure 4.Editors sketch drawing of the Lotus twin cam engine
The versatility of the Twin cam was that it was adopted in both road and competition cars in both front and mid-engine configuration. It excelled in diverse competition that included sports and sports racing through to international rally.
We include a selection of photographs and drawings as examples and we invite subscribers to explore further examples.
Bacon “Lotus” and particularly Ludvigsen “Colin Chapman” have some excellent photographs of Twin Cam installations uncluttered by bodywork. Ludvigsen devotes a chapter on engines entitled “Engine Enterprise” which is really appropriate. Not only does he include useful analysis he provides engineering drawings of engines installed in the chassis. One of the best is that of the Elan and it reinforces the totality and exceptional packaging of the Elan – the twincam engine, the backbone chassis and two seater bodywork.
Our learning /educational opportunities are intended to be challenging thought provoking and requiring additional research and/or analysis.
These opportunities are particularly designed for a museum/education centre location where visitors would be able to enjoy access to all the structured resources available in conjunction with any concurrent exhibition.
In this instance we suggest the following might be appropriate:-
- To which Lotus models was the Twin Cam fitted, which was most successful and why?
- Enumerate non Lotus adoption of the Twin Cam – what were advantages/disadvantages?
- List other famous twin cam engines
- Discover what is the weight of the Lotus twin cam engine and its physical dimensions
- Who are the current twin cam specialists/ engineers and parts suppliers
- Establish the production numbers of the Lotus twin cam compare this with peers
- Compare and contrast the closest equivalent Coventry climax engine and the Lotus twin cam
- Identify any reliability or design weaknesses / construction, how can these be overcome
- Discuss the significance of the Lotus Twin cam engine on sales? Can you think of an alternative in period?
- Debate “Chapman the exponent of added value”
- Use drawing as template to construct cross section, produce 3 view working type drawing or add ancillaries. Consider how the design was suitable for various installations.
- What sort of contract did Chapman negotiate to buy engine block as and in what volume?
- Do you consider that Colin Chapman might have tried to persude Ford to build the twin cam in total and in volume and sell these to him?
Editors sketch of Twin cam in the Lotus 23 cf installation with that of Lotus Europa
Exhibitions, Education and Economics
In the museum context the editors believe that commercial considerations are both necessary and complementary with its educational objectives.
For these reasons our suggested outline Business Plan includes provision for promoting products and services which share Chapman’s ideals of mechanical efficiency and sustainability. In addition we propose merchandising that explain and interprets the social and cultural context of Chapman’s designs in period. It’s suggested there will be catalogue for on line purchasing.
The Twin Cam engine provides many exhibition opportunities and ready titles include:-
- Cams,Comaraderie and Consultancy
- Cams on Camera
- Block and Tackle
- The Engine of Change :Chapman and the Lotus Twin Cam
- Chapman’s Reciprocating Engine
- Chapman’s Compound Engine
- Chapman gets the Timing right
- Mods and Rockers: Chapman and engine conversions
- Colin Chapman :Engine Driver
- Lotus and the Input-Output Equation
Many educational opportunities exist from mathematics to marketing. The editors consider those of Industrial Product design the most useful and relevant to emerging designers and entrepreneurs.
The editors refer to Colin Chapman as a polymath. We believe the achievements of this remarkable engineer exist because of his integrating and indivisibility of skills and aptitudes. These include his determination, creativity, resourcefulness, ambition, business acumen and personal charisma.
When these combined they made an indomitable spirit dedicated to finding solutions.
In our study of the Twin Cam engine we see the particular interaction of:-
- Industrial designer [seeking added value]
Because Chapman was without ego it allowed him to be totally pragmatic and the Lotus Engineering Policy quoted above reminds us of this focus on reality and necessity.
There were advantages and disadvantages to Lotus being an engine manufacturer in the early days.
Chapman created a specialist marque with an extreme added value and aesthetic .The fact he used a proprietary engine for many customers was a bonus. To these engines and certainly in the case of the Twin Cam he added value. In many respects the twin cam was a step on the road to outright manufacture. Its inclusion in international competition raised its profile and established a performance reputation and of course assisted sales both for Lotus and Ford.
This unit was fully appropriate, economic, effective etc. for the product, customer and times.
Many other specialist marques from around the world have made their reputations adopting and upgrading mainstream engines. Amongst these are Abarth, Cobra, TVR, Marcos, Caterham and Morgan and of course many of the current generation of kit car makers.
The Lotus Twin Cam was produced in relatively large numbers and powered an array of machinery –road, track, sports, saloon etc.
The Twin Cam is a particularly good example of Industrial Designers in the art and science, economics of creating added value through a product made effective and affordable.
Although with a few engineering weaknesses the Twin Cam was an effective solution and in its own right a significant piece of engineering architecture and aesthetics. In the editors estimation if fulfilled an engineer’s requirement of form and function and the Chapman design philosophy of effectiveness and economy.
The Twin Cam is one of the many occasions when Chapman brought into existence a significant product where he brought together his resolve to:-
Subscribers might like to compare the gestation of the Ford Cosworth DFV and the Ford Lotus Twin Cam there are some interesting and powerful overlaps. In both cases Chapman brought forward engines that democratized and strengthened the sport and ownership of iconic vehicles. He simultaneously raised the reputation of Lotus and Ford.
In automobile history there are few that achieved or exercised so much improvisation at the affordable end of the market.
Lotus Twin Cam Engine.Wilkins.Brooklands.1988.
Legendary Car Engines.Simister.Motorbooks.2004.
Motor Sports Car Road Tests. Temple Press.1965
Subscribers might like to note we hold an extensive range of books specific to the Elan and Europa. Please ask for details.
Please note the editors of the A&R attempt to give the broadest spectrum of references but not all are available for consultation in an article. However by noting their existence it may assist students in their research.
*Items in italics non A&R library books.