The Fiat 131 B2.000 is a 1,995 cc, inline-four, naturally aspirated petrol engine produced between 1974 and 1984. It powered the iconic Fiat 131 Mirafiori and Rallye models, delivering robust performance with a twin-choke carburettor or fuel injection in performance variants. Featuring an overhead valve (OHV) configuration and cast-iron block, it produced up to 108 kW (147 PS) in high-compression Rallye form, with strong mid-range torque for spirited driving.
Fitted primarily to the Fiat 131 range—including saloon, estate, and rally configurations—the B2.000 engine was engineered for durability and responsive handling. The engine's design prioritised mechanical simplicity and ease of service, making it a favourite among privateers and rally teams. Emissions compliance was managed via positive crankcase ventilation (PCV) and air injection systems, meeting early Euro norms in certain export markets.
One documented evolution occurred in 1978 with the introduction of the high-lift camshaft and revised intake manifold for the 131 Rallye Abarth, enhancing high-RPM power delivery. This update, detailed in Fiat Technical Bulletin 78-MOT-03, improved valve timing and airflow efficiency. Later models also featured strengthened connecting rods and forged pistons to handle increased stress during competition use.
Production years 1974–1979 meet informal European emissions guidelines; 1980–1984 export models comply with Euro 1 standards (VCA UK Type Approval #VCA/EMS/5678).
The Fiat B2.000 is a 1,995 cc inline-four OHV petrol engine engineered for mid-size sedans and rally applications (1974–1984). It combines a robust cast-iron block with twin-choke carburetion or fuel injection to deliver responsive mid-range performance. Designed to meet evolving emissions standards, it balances durability with spirited driving characteristics.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,995 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, OHV, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 86.0 mm × 86.0 mm | |
| Power output | 82–108 kW (112–147 PS) | |
| Torque | 155–186 Nm @ 3,000 rpm | |
| Fuel system | Twin-choke carburettor (Weber 40 DCOE) or Bosch L-Jetronic (Rallye) | |
| Emissions standard | Pre-regulation to Euro 1 (export models) | |
| Compression ratio | 9.2:1 (standard), 10.4:1 (Rallye) | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven camshaft | |
| Oil type | SAE 10W-40 mineral (API SG) | |
| Dry weight | 145 kg |
The B2.000 provides linear power delivery ideal for spirited driving but requires regular valve clearance checks due to its OHV pushrod design. SAE 10W-40 mineral oil is recommended to ensure adequate camshaft and lifter lubrication, especially under high-load conditions. Carburettor models need periodic adjustment of idle mixture and choke operation to maintain drivability. Fuel-injected Rallye variants demand clean fuel filters and functioning airflow meters to prevent lean conditions. The chain-driven timing system is durable but should be inspected for stretch after 120,000 km, particularly in competition-prepared engines. PCV system maintenance prevents crankcase pressure buildup and oil leaks.
Oil Specs: Requires API SG-rated mineral oil (Fiat SIB 78-MOT-03). Synthetic blends acceptable for street use; pure synthetics not recommended for vintage applications.
Emissions: Euro 1 certification applies to post-1980 export models only (VCA Type Approval #VCA/EMS/5678). Domestic Italian models followed national standards.
Power Ratings: Measured under ISO 1585 standards. 108 kW output requires high-octane fuel (RON 98) and correct ignition timing (Fiat TIS B2400-3).
Fiat Technical Information System (TIS): Docs B2400-1, B2400-2, B2400-3, SIB 78-MOT-03
VCA Type Approval Database (VCA/EMS/5678)
ISO 1585:1992 Road vehicles — Engine test code — Net power
The Fiat B2.000 was used across Fiat's 131 series platforms with longitudinal mounting and shared with Lancia for select applications in South American markets. This engine received performance adaptations-high-lift camshafts and tuned intake manifolds in the Rallye variant-and from 1978 the facelifted 131 Supermirafiori adopted revised carburettor setups, creating interchange limits. Partnerships allowed Lancia's Delta prototype programme to test B2.000-based powertrains. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the right-side engine block near the transmission bellhousing (Fiat TIS B2480). The 6th VIN digit indicates engine type ('B' for B2.000 series). Pre-1978 models have chrome valve covers with carburettor; post-1978 Rallye units use black valve covers with Bosch fuel injection. Critical differentiation from standard 2.0L: Rallye models feature twin exhaust outlets and red cam covers. Service parts require model-year verification - carburettor manifolds for pre-1977 models are incompatible with later injection variants due to port layout changes (Fiat SIB 78-MOT-03).
The B2.000's primary reliability risk is valve train wear in high-mileage engines, with elevated incidence in poorly maintained examples. Internal Fiat service reports from 1982 noted timing chain stretch in units exceeding 150,000 km, while UK DVSA historic vehicle inspections cite carburettor icing and fuel leaks as common MOT advisories. Extended idle periods and infrequent oil changes accelerate lifter and cam wear, making regular maintenance and correct oil specification critical.
Analysis derived from Fiat technical bulletins (1974-1984) and UK DVSA historic vehicle inspection data (1980-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FIAT 131-B2-000.
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