Alfa Romeo's in-house V6 engine design made its initial début in 1979 in the Alfa 6. Introduced in 2.5 L guise, production engines would eventually range from 2.0 L to 3.2 L displacement. With modifications it is possible to increase engine displacement to 3.8 L (232 cu in). Initially developed in the early 1970s by Giuseppe Busso, the original SOHC 12-valve design employed short push-rods to operate the exhaust valves in a design similar to that of earlier Lancia Fulvia engines. In 1993, the first DOHC version of this engine appeared powering the Alfa Romeo 164. The engine is an aluminium alloy block and head with sodium filled exhaust valves to avoid overheating. The South African market introduced the 3.0 L GTV-6, predating the international debut of the factory's own 3.0 L engine in 1987.
A 2.0 L (1,997 cc (121.9 cu in)) version was introduced in 1983. Both carburettor 132 PS (97 kW; 130 hp) and fuel-injected versions were available from the start. A 2.0 turbocharged version, derived from the 3.0 L 12v, was introduced in 1991 in the Alfa Romeo 164 with 210 PS (154 kW; 207 hp). The engine has a 80.0 mm (3.15 in) bore and a 66.2 mm (2.61 in) stroke.
1983–1986 Alfa Romeo Alfa 6
1984–1987 Alfa Romeo 90
1991–1997 Alfa Romeo 164 (2.0 L turbo)
1995–2001 Alfa Romeo GTV & Spider (2.0 L turbo)
1998–2002 Alfa Romeo 166 (2.0 L turbo)
The original engine displaced 2.5 L (2,492 cc (152.1 cu in)) and produced 158 PS (116 kW; 156 hp). It was a 2-valve-per-cylinder design with a single belt-driven camshaft per cylinder bank and six carburettors fitted.
Fuel injection was added for the 1983 Alfa 6, which produced the same 158 PS (116 kW; 156 hp). The 2-valve engine ended its life in the Alfa 155, where there were two series for this engine, the 2.5 L developing 166 PS (122 kW; 164 hp). Differences between them were small and only on torque and power delivery producing exactly the same horsepower.
1979–1986 Alfa Romeo Alfa 6
1980–1986 Alfa Romeo GTV6
1984–1987 Alfa Romeo 90
1985–1991 Alfa Romeo 75/Milano
1992–1997 Alfa Romeo 155
1985–1996 Fiat Croma
1987–1989 Rayton Fissore Magnum V6
A four-valve version was introduced in 1997 with the Alfa Romeo 156. The engine now produced 190 PS (140 kW; 187 hp). In 2001, the V6 was uprated to 192 PS (141 kW; 189 hp). The 166 used a slightly detuned version to make more low rev torque. This engine version was awarded as the International Engine of the Year in 2000. The engine has a 88 mm (3.5 in) bore and a 68.3 mm (2.69 in) stroke.
1997–2005 Alfa Romeo 156
1998–2007 Alfa Romeo 166
The 2.5 L engine was bored and stroked out to 3.0 L by Alfa racing in South Africa, in 1985(2,959 cc (180.6 cu in))and used for the 1987 75/Milano Verde, where it produced 185 PS (136 kW; 182 hp), still with 2 valves per cylinder. This engine was modified for transverse placement in the 164 and fitted with a high-performance camshaft and low-restriction exhaust, producing 192 PS (141 kW; 189 hp) in standard form, 184 PS (135 kW; 181 hp) when a catalyzer was fitted in 1991, with the Cloverleaf version producing 200 PS (147 kW; 197 hp). The same engine fitted to the SZ was tuned to a further 210 PS (154 kW; 207 hp). The engine has a 93 mm (3.7 in) bore and a 72.6 mm (2.86 in) stroke.
1985–1989 Alfa Romeo GTV6
1987–1991 Alfa Romeo 75/Milano
1989–1991 Alfa Romeo SZ
1992–1994 Alfa Romeo RZ
1992–1994 Lancia Thema
1988–1997 Alfa Romeo 164
1995–2001 Alfa Romeo Spider
The engine was upgraded to dual overhead cams and four valves per cylinder in 1993. Due to this and other refinements, this engine produced 211 PS (155 kW; 208 hp) for the regular 1993 164, with 230 PS (169 kW; 227 hp) and 276 N·m (204 ft·lbf) in the 164 QV with the Euro 3 engine producing 232 PS (171 kW; 229 hp) on the Q4 model which in its final production run in 1996, it got reduced to 228 PS (168 kW; 225 hp) but with increased torque. The final run of 3.0 V6 engines fitted to the GTV and 166 range, produced 220 PS (162 kW; 217 hp).
1992–1997 Alfa Romeo 164
1997–2003 Alfa Romeo GTV & Spider
1998–2005 Alfa Romeo 166
1994–2001 Lancia Kappa
2001–2002 Lancia Thesis
1998–present Gillet Vertigo (Vertigo used also 3.6 L version)
In 2002 Alfa Romeo introduced the 156 GTA with a 3.2 L (3,179 cc (194.0 cu in)) version of the V6 with 250 PS (184 kW; 247 hp) and 300 N·m (220 ft·lbf) of torque. Later this engine was also used in the Alfa Romeo 166, GTV, Spider and Alfa Romeo GT in a slightly detuned form 240 PS (177 kW; 237 hp). The engine has a 93 mm (3.7 in) bore and a 78 mm (3.1 in) stroke.
2002–2005 Alfa Romeo 156 GTA
2002–2005 Alfa Romeo 147 GTA
2004–2007 Alfa Romeo GT
2003–2005 Alfa Romeo 166
2003–2005 Alfa Romeo GTV & Spider
2003–2006 Lancia Thesis
The V6 production ended in 2005 at Alfa Romeo Arese Plant; a stock of five thousand was built, to be used in Lancia Thesis, Alfa 166 and Alfa GT models. The engine was replaced in the 159 and Brera by a new 3.2 L V6 unit combining a General Motors-designed engine block with Alfa Romeo cylinder heads and induction. British automotive engineering company Cosworth was keen to buy assembly lines of the Alfa Romeo V6 engine, but the Italian company did not want to sell it. The last version of 3.2 L engine was Euro4 compliant, so it would have been possible to produce it a couple of years more. The engine designer Giuseppe Busso died only a couple of days after the last engine was produced in Arese.