The 420 was launched in 1985, two years after the 425. It was simply the same car overall, only with the 2.0L V6 in place of the 2.5L unit. This model was meant primarily for the Italian market, where cars with engines over two litres of capacity were heavily taxed by the government during the 1980s. Introduced simultaneously with the 420, the sportier 420 S saw its power output raised by 30hp to reach an impressive 210hp for an engine with two-litre of capacity. This increase was due in great part to the use of twin air-to-air intercoolers, the presence of which was given away by two NACA ducts on the bonnet. The model was very similar to the Biturbo S, only with four doors and the implied longer wheelbase. Hence the body followed the same treatment with a two-tone paint scheme (silver or red over grey lower-body) and blacked-out chrome trim. The interior was trimmed by hand in red leather, deployed on the central part of the seats, centre console, dashboard and armrests. From 1986, the 420 adopted a Weber fuel injection system, thus becoming the 420i. The car was otherwise unchanged, save for minor improvements to the suspension system.
| Data sheet | 420 | 420 S | 420i | 420 Si |
|---|---|---|---|---|
| Model code | Tipo AM332 | Tipo AM332 | Tipo AM332 | Tipo AM332 |
| Body type | 4-door, 5-seater saloon | 4-door, 5-seater saloon | 4-door, 5-seater saloon | 4-door, 5-seater saloon |
| Design | Pierangelo Andreani | Pierangelo Andreani | Pierangelo Andreani | Pierangelo Andreani |
| Production years | 1985 - 1986 | 1985 - 1987 | 1986 - 1988 | 1986 - 1988 |
| Maserati era | De Tomaso | De Tomaso | De Tomaso | De Tomaso |
| Numbers produced | 1,686 | 254 | 1,124 | 524 |
| Chassis | Monocoque steel construction | Monocoque steel construction | Monocoque steel construction | Monocoque steel construction |
| Dry weight | 1,180kg | 1,180kg | 1,180kg | 1,180kg |
| Engine configuration | 90° V6, three valves per cylinder (two intake, one exhaust), single overhead camshaft, twin-turbo | 90° V6, three valves per cylinder (two intake, one exhaust), single overhead camshaft, twin-turbo | 90° V6, three valves per cylinder (two intake, one exhaust), single overhead camshaft, twin-turbo | 90° V6, three valves per cylinder (two intake, one exhaust), single overhead camshaft, twin-turbo |
| Displacement | 1,996cc | 1,996cc | 1,996cc | 1,996cc |
| Maximum power | 180hp @ 6,000rpm | 210hp @ 6,500rpm | 190hp @ 6,000rpm | 220hp @ 6,350rpm |
| Top speed | 215km/h | 218km/h | 220km/h | 228km/h |
