Lotus-Ford Twin Cam
Encyclopedia
The Lotus-Ford Twin Cam is a 1558 cc engine developed for the 1962 Lotus Elan
Lotus Elan
Lotus Elan is the name of two convertible cars and one fixed head coupé produced by Lotus Cars. The original Type 26, 26R Racing version , 36R Racing version , 36 Fixed Head Coupe, 45 Drop Head Coupe, and the "Type 50" +2 Coupe, circa 1962 to 1975, are commonly known as the '60s Elans...

 and also used in a variety of other vehicles up until mid 1970s.

Design

Lotus
Lotus Cars
Lotus Cars is a British manufacturer of sports and racing cars based at the former site of RAF Hethel, a World War II airfield in Norfolk. The company designs and builds race and production automobiles of light weight and fine handling characteristics...

 required a low cost, compact, yet powerful engine for the 1962 Lotus Elan
Lotus Elan
Lotus Elan is the name of two convertible cars and one fixed head coupé produced by Lotus Cars. The original Type 26, 26R Racing version , 36R Racing version , 36 Fixed Head Coupe, 45 Drop Head Coupe, and the "Type 50" +2 Coupe, circa 1962 to 1975, are commonly known as the '60s Elans...

. Colin Chapman
Colin Chapman
Anthony Colin Bruce Chapman CBE was an influential British designer, inventor, and builder in the automotive industry, and founder of Lotus Cars....

 chose to use the 116E thin wall cast iron block first used by Ford
Ford Motor Company
Ford Motor Company is an American multinational automaker based in Dearborn, Michigan, a suburb of Detroit. The automaker was founded by Henry Ford and incorporated on June 16, 1903. In addition to the Ford and Lincoln brands, Ford also owns a small stake in Mazda in Japan and Aston Martin in the UK...

 in the Consul Classic, the Classic Capri and later to be used in the Cortina. While the basic engine design was relatively sound, being of 5 main bearing construction, it was by no means a performance engine. To achieve the power required, Chapman commissioned Harry Mundy
Harry Mundy
Harry Mundy was a British car engine designer and motoring magazine editor.He was educated at King Henry VIII School in Coventry and went on to serve his apprenticeship with Alvis. He left them in 1936 to join English Racing Automobiles in Bourne, Lincolnshire as a draughtsman...

, then technical editor for Autocar
Autocar
Autocar is a weekly British automobile magazine published by Haymarket Motoring Publications Ltd. It refers to itself as "The World's oldest car magazine".-History:...

 magazine, to design a double overhead camshaft conversion. This comprised an aluminium cylinder head and an aluminium front cover assembly containing the water pump and the chain driven camshaft drive.

In its initial evolution the engine had a cubic capacity of 1498 cc and produced approximately 100 bhp. After approximately 50 engines had been produced (only 22 engines of this initial specification made their way into roadgoing Elans, the rest being used in the Lotus 23) the specification was changed so the engine had a 0.060" larger bore dimension as standard thereby increasing the cubic capacity to 1558 cc. This enabled an overbore of 0.040" permitted by the FIA
Fédération Internationale de l'Automobile
The Fédération Internationale de l'Automobile is a non-profit association established as the Association Internationale des Automobile Clubs Reconnus on 20 June 1904 to represent the interests of motoring organisations and motor car users...

 regulations would still mean a cubic capacity below the new 1600 cc FIA class limit.

Technical

The 1558 cc twincam engine has internal dimensions as follows

3.250 inches (82.55 mm) bore

2.900 inches (72.746 mm) stroke

The 116E block was used in 5 basic versions
The Mark 1 - from 1962 to 1967
The -6015 block with round main bearing caps and 4 bolt crankshaft

The Mark 2 - from 1967-1975
The 3020-6015 block with round main bearing caps and 6 bolt crankshaft
The 681F-6015 block with round main bearing caps and 6 bolt crankshaft
The 681F-6015 block with square main bearing caps and 6 bolt crankshaft
The 701M-6015 block with square main bearing caps and 6 bolt crankshaft


The cylinder head has hemispherical combustion chambers similar to that first used by Peugeot
Peugeot
Peugeot is a major French car brand, part of PSA Peugeot Citroën, the second largest carmaker based in Europe.The family business that precedes the current Peugeot company was founded in 1810, and manufactured coffee mills and bicycles. On 20 November 1858, Emile Peugeot applied for the lion...

 on their 1912 Grand Prix car and subsequently refined by Jaguar
Jaguar (car)
Jaguar Cars Ltd, known simply as Jaguar , is a British luxury car manufacturer, headquartered in Whitley, Coventry, England. It is part of the Jaguar Land Rover business, a subsidiary of the Indian company Tata Motors....

 in their XK engine of the 1950s

Valve sizes used are 1.530" diameter inlet and 1.325" diameter exhaust on all engines except the "big valve" Elan Sprint and Lotus Europa models which have an inlet valve measuring 1.565" diameter.

Applications

  • 1962-1974 Lotus Elan
    Lotus Elan
    Lotus Elan is the name of two convertible cars and one fixed head coupé produced by Lotus Cars. The original Type 26, 26R Racing version , 36R Racing version , 36 Fixed Head Coupe, 45 Drop Head Coupe, and the "Type 50" +2 Coupe, circa 1962 to 1975, are commonly known as the '60s Elans...

  • 1963-1970 Lotus Cortina
    Lotus Cortina
    The Lotus-Cortina is a high-performance car, which was produced in the United Kingdom from 1963 to 1970 by the Ford in collaboration with Lotus Cars. The original version, which was based on the Ford Cortina Mark 1, was promoted by Ford as the "Consul Cortina developed by Lotus", with "Consul"...

  • 1968-1970 Ford Escort Twin Cam
  • 1971-1975 Lotus Europa
    Lotus Europa
    The Lotus Europa was a two door mid-engined GT coupé built by Lotus Cars from 1966 to 1975. In 2006 Lotus began production of a totally new, Lotus Elise-derived design, a mid-engined GT coupé named Europa S....

  • 1973-1974 Lotus Seven
    Lotus Seven
    The Lotus Seven is a small, simple, lightweight two-seater open-top sports car produced by Lotus Cars between 1957 and 1972....


Motorsport

The Lotus Twin Cam is an enduring engine and even to this day is still used in rallying, hillclimbing, autocross and of course, historic motorsport events. In fact, some may argue that the "twink" is more popular in motorsport now than it was during its production. This, in no small part, is due to the likes of companies such as QED Motorsport who strive to keep the engine in service with hard or impossible to find engine components. QED even bought the license to officially re-produce the Twin Cam's cylinder head.

Power output

The power output for roadgoing versions are as follows (official figures as claimed by Lotus)

100 bhp Elan 1500

105 bhp Elan 1600, S2, S3

105 bhp Elan S4

115 bhp Elan S2 S/E, S3 S/E, S4 S/E

118 bhp Late Elan S3 S/E

126 bhp Elan Sprint
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