Lotus-Ford Twin Cam

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The Lotus-Ford Twin Cam is a 1558 cc engine used predominantly on the Lotus Elan model during the 1960's and early 1970's.

Contents

[edit] Design

Lotus required a low cost, compact, yet powerful engine for the 1962 Lotus Elan which led Colin Chapman to use the 116E thin wall cast iron block first used by Ford in the Consul Classic, the 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, then technical editor for Autocar 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 (75 kW). 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 regulations would still mean a cubic capacity below the new 1600 cc FIA class limit.

[edit] 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 701F-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 on their 1912 Grand Prix car and subsequently refined by Jaguar in their XK engine of the 1950's

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.

[edit] Applications

The same engine was used in both the Mark 1 Lotus Cortina and the Mark 2 Cortina Lotus, the Ford Escort Twin Cam, the Lotus Elan +2 and the last Lotus Sevens. It was also used in later versions of the Lotus Europa.

  • 1962-1974 Lotus Elan
  • 1963-1970 Lotus Cortina
  • 1968-1970 Ford Escort Twin Cam
  • 1971-1975 Lotus Europa
  • 1973-1974 Lotus Seven

[edit] Power Output

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

100 bhp (75 kW) Elan 1500
105 bhp (78 kW) Elan 1600, S2, S3
105 bhp (78 kW) Elan S4
115 bhp (86 kW) Elan S2 S/E, S3 S/E, S4 S/E
118 bhp (88 kW) Late Elan S3 S/E
126 bhp (94 kW) Elan Sprint

[edit] Production Quantities

Approximately 34,000