Lotus-Ford Twin Cam

The Lotus-Ford Twin Cam is a 1558 cc engine developed for the 1962 Lotus Elan and also used in a variety of other vehicles up until mid 1970's.

Design

Lotus required a low cost, compact, yet powerful engine for the 1962 Lotus Elan. Colin Chapman chose 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 convert|100|bhp|abbr=on. 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.

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

Power Output

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

convert|100|bhp|abbr=on Elan 1500
convert|105|bhp|abbr=on Elan 1600, S2, S3
convert|105|bhp|abbr=on Elan S4
convert|115|bhp|abbr=on Elan S2 S/E, S3 S/E, S4 S/E
convert|118|bhp|abbr=on Late Elan S3 S/E
convert|126|bhp|abbr=on Elan Sprint

Production Quantities

Approximately 34,000