While the 105E block only provided three main bearings for the crankshaft, the oversquare design kept piston speeds down and gave room for larger valves in the new cylinder head.

When the larger 1.3 L; 81.7 cu in (1,339 cc) 109E for the Ford Consul Classic was released, it became the platform for most of the development of the new Lotus engine.

After the initial design was finished, outside consultant Richard Ansdale produced detailed drawings of the new cylinder head.

Lotus employee Steve Sanville headed the production engineering team that included Mike Costin, Neil Francis and Bob Dance.

The first test vehicle to receive a Twin Cam was a left hand drive Ford Anglia, and the engine was installed on 18 January 1962.

This Anglia is reported to have overtaken a Jaguar at well over 100 mph (160 km/h) in the hands of Jim Clark on his way home to Scotland from Goodwood.

[9] After building a limited number of 1.5 L Twin Cams, the bore was increased to 82.55 mm (3+1⁄4 in), raising the capacity to 1.56 L. Assembly of the first 50 engines was contracted out to J.A.Prestwich.

This allowed the Twin Cam to be over-bored by up to 1 mm (0.04 in) and still remain below the 1600 cc class limit permitted by FIA regulations.

The intake manifold was a series of short tubular stubs cast as an integral part of the cylinder head.

[12] Early Lotus blocks were simply standard Ford production line items selected for having the thickest cylinder walls, and were identified by an "A" stamped into the timing cover mating face.

The Twin Cam had a problem with oil surge, and the attachment of the starter motor was subject to flexing when trying to spin the high-compression engine.

Early engines had the word "Lotus" in script cast in raised letters on the cam cover above each camshaft.

[1] Lotus began to offer more highly tuned Special Equipment engines as options in their cars.

Power was estimated to be 124–126 bhp (92.5–94.0 kW), fully three years prior to the release of the Big Valve engine.

The Big Valve Twin Cam was a project of Lotus' Engineering Director Tony Rudd.

[1] Rudd reduced the deck height by 0.04 in (1.0 mm) to raise the compression ratio to 10.5:1, increased the diameter of the inlet valves to 1.565 in (39.8 mm), modified the inlet runners' shape for the larger valves and installed Super Special Equipment D-type camshafts.

The majority of the power gain comes from modifying the size and shape of the intake runners (porting) and fitting uprated camshafts.

Their new company developed the Twin Cam for competition use under Cosworth Project Code TA, with specific versions designated with an 'Mk.'

The proliferation of the Mk.XIII triggered the establishment of new European-style racing-engine builders in the US performing rebuilding and maintenance work needed on the Mk.XIII while also contributing to Cosworth's revenue.

This was followed by a gear-driven DOHC 4-valve cross-flow aluminium head on the same block with a Mk.XIII forged crank for a new 1.6 Liter Formula 2 engine named the FVA in 1966.

The Twin Cam made its racing debut in May 1962 as a Cosworth Mk.X in a Lotus 23 driven by Jim Clark at the Nürburgring.

Cosworth Mk.XV powered the Elan 26R of the Willment Team and driver John Miles to 15 seasonal wins and the 1966 Autosport Championship title.

Early tuners included Holbay, Vegantune, and Novamotor, joined later by Brian Hart, Richardson, Wilcox and others who focused mainly on the Formula classes.

Roger Barr won the 1968 US Formula B National Championship using a Twin Cam, with numerous modifications made to both it and the Crossle chassis.