Alfa Romeo Twin Cam engine

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Alfa Romeo Twin Cam

Alfa Romeo Twin Cam engine
Manufacturer	Alfa Romeo
Production	1954–1994
Successor	Alfa Romeo TwinSpark
Class	DOHC 2-valve I4
Engine	1.3 L (1290 cc/78 in³) 1.6 L (1570 cc/95 in³) 1.8 L (1779 cc/108 in³) 2.0 L (1962 cc/119 in³)

The all alloy Alfa Romeo Twin Cam engine series was a inline-4 cylinder engine produced by Alfa Romeo from 1954 to 1994. For earlier Alfa Romeo engines featuring twin camshafts, refer to the main Alfa Romeo page. For the later Twin Spark engines which also feature twin camshafts, and are based on a Fiat designed engine block, please refer to the Alfa Romeo Twin Spark engine page.

[edit] History

The Alfa Romeo Twin Cam engine was introduced in the 1290 cc Giulietta of 1954. The features of the Giulietta engine included:

Aluminium alloy engine block with cast-iron cylinder liners
Aluminium alloy cylinder head with hemispherical combustion chambers
Forged steel crankshaft running in five main bearings
Double overhead camshafts driven by a double row timing chain
Camshafts directly actuate valves via bucket tappets
Two inclined valves per cylinder with near central located spark plug
Inlet and exhaust valves separated by an angle of 80 degrees

This made the Alfa Romeo Twin Cam engine an advanced design for a production car of the mid 1950s. These design features, with minor variations, would form the basis of all future versions of the engine. The capacity was increased to 1570 cc with the introduction of the Giulia in 1962. Racing versions of the Giulia engine, include the twin plug engine used in the GTA which featured a cylinder head with two spark plugs per cylinder.

The twin cam engine was later increased to 1779 cc for the 1750 GTV and Berlina in 1968. The 1962 cc engine was introduced in 1971 for the 2000 GTV and Berlina 2000. Twin spark plug versions of the 1750 and 2000 were used for racing and there were a limited number of racing engines fitted with a 16 valve cylinder head.

In 1986, a turbocharged version of the 1779 cc single plug engine was fitted to the Alfa Romeo 75, providing 155 bhp in standard form and a potential for a power output of 300 bhp in Group A touring car racing form.

In 1987, the Alfa Romeo 75 was fitted with a twin spark plug per cylinder head design, which provides improved fuel ignition and allows an improved combustion chamber shape with narrower angle between intake and exhaust valve. This was combined with variable valve timing and electronic fuel injection to give a power output of 148 bhp.

Production of the Alfa Romeo Twin Cam ended in 1994, by which time it had been superseded by the newer 16 valve Twin Spark engine.