The Lancia Flat-4 engine is an aluminum, pushrod flat-four (boxer) engine made by Lancia for the Flavia from 1960 through 1984. Though it was a pushrod engine, it was advanced for the time.[1] The pushrod version of the Lancia boxer was only ever used in the Flavia, and its derivatives including the Lancia 2000. In 1976, a new overhead cam engine based on a similar layout was designed and brought into production in 2 and 2.5-litre displacements for the Gamma.
| Flat-4 engine | |
|---|---|
Boxer engine installed in a Lancia Flavia | |
| Overview | |
| Production | 1960-1984 |
| Layout | |
| Configuration | Naturally aspirated Flat-4 |
| Displacement |
|
| Cylinder bore |
|
| Piston stroke |
|
| Block material | Light alloy |
| Head material | Aluminum |
| Valvetrain | Pushrod or Overhead camshaft |
| Combustion | |
| Fuel system |
|
| Fuel type | Petrol |
| Cooling system | Water-cooled |
| Output | |
| Power output | 92–140 bhp (69–104 kW; 93–142 PS) |
| Torque output | 172–208 N⋅m (127–153 lb⋅ft) |
| Chronology | |
| Predecessor | Lancia V4 engine |

The original version was the 1.5 L; 91.5 cu in (1,500 cc) introduced in 1960; it used an 82 mm × 71 mm (3.23 in × 2.80 in) bore and stroke. It was revised on 1963 with a smaller 80 mm (3.15 in) bore and a longer 74 mm (2.91 in) stroke, thus displacing 1.5 L; 90.8 cu in (1,488 cc). A final version was introduced in 1967 with an even longer 80 mm (3.15 in) stroke coupled with a 77 mm (3.03 in) bore, giving a displacement of 1.5 L; 90.9 cu in (1,490 cc). Production ceased in 1970.
The first 1800 was a 1.7 L; 105.4 cu in (1,727 cc) introduced in 1962. It used an 88 mm × 71 mm (3.46 in × 2.80 in) bore and stroke. One year later it was replaced by a true 1.8 L; 109.8 cu in (1,800 cc) engine thanks to a longer 74 mm (2.91 in) stroke. In 1967 appeared the 1.8 L; 110.8 cu in (1,816 cc) version using an 85 mm × 80 mm (3.35 in × 3.15 in) bore and stroke.
The 2.0 L; 121.5 cu in (1,991 cc) 2000 version was the ultimate Flavia engine. Bore and stroke was 89 mm × 80 mm (3.50 in × 3.15 in) for a good oversquare ratio. In 1971, the 2.0 L produced 115 bhp (86 kW; 117 PS),[citation needed] and in the HF Coupé in 1972 it produced 125 bhp (93 kW; 127 PS). This engine was produced from 1968 through 1974.
Lancia developed the large light-alloy overhead camshaft 2.0-litre and 2.5-litre flat-4 engines specifically for the Lancia Gamma, rather than using Fiat derived engines as used in the Beta and Montecarlo and were in production between 1976 and 1984.
Replacing the 2.0 L pushrod engine used in the Flavia, the new 2.0 L; 122.0 cu in (1,999 cc) OHC engine produced 120 bhp (89 kW; 122 PS) at 5500 rpm[2] and 172 N⋅m (127 lb⋅ft) of torque at 3500 rpm.
The 2.5 L; 151.6 cu in (2,484 cc) engine was initially available with twin-choke Weber carburetors, but in the last few years of production it was equipped with fuel injection. In both forms, it produced 140 bhp (104 kW; 142 PS) at 5400 rpm and 208 N⋅m (153 lb⋅ft) torque at 3000 rpm.[3]
Lancia's four has its cylinders horizontally-opposed, à la Porsche (or VW Beetle if you're uncharitable)--except it's water-cooled, hanging out over the nose, and driving the front wheels. Power, even at 92 bhp (69 kW; 93 PS), was far beyond VW's modest output in those days, even allowing for the displacement discrepancy.
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