The Fiat 131 AZ.000 is a 1,592 cc inline-four petrol engine produced between 1974 and 1984. It powered the Fiat 131 Mirafiori and Rallye models, delivering 65–75 kW (88–102 PS) depending on tune. Featuring a cast-iron block, belt-driven SOHC, and twin-choke carburettor in higher-output versions, it was engineered for durability and serviceability in both family and competition applications.
Fitted to the Fiat 131 range—including saloon, estate, and rally variants—the AZ.000 was designed for balanced performance and fuel economy in European driving conditions. Its robust architecture supported factory rally development, with mechanical fuel injection introduced in Group 4 rally trim. Emissions compliance was managed via controlled combustion and early evaporative canister systems, meeting pre-Euro baseline standards applicable to its era.
One documented engineering update occurred in 1978, referenced in Fiat Service Bulletin AZ-78-01, involving revised valve stem seals to reduce oil consumption in high-mileage engines. This update improved long-term reliability and was retrofittable to earlier builds, reflecting Fiat's iterative development approach during the engine's decade-long production run.
Production years 1974–1984 comply with pre-Euro European emissions directives (EEC 70/220) as implemented in Italy and EU markets (Italian Ministry of Transport Type Approval #MIT/74/AZ000).
The Fiat AZ.000 is a 1,592 cc inline-four petrol engine engineered for mid-size sedans and rally applications (1974–1984). It combines SOHC valvetrain architecture with carburettor or mechanical injection to deliver reliable power delivery and mechanical simplicity. Designed to meet early emissions regulations, it balances durability with serviceability for both daily use and motorsport.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,592 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 80.0 mm × 79.5 mm | |
| Power output | 65–75 kW (88–102 PS) | |
| Torque | 124–132 Nm @ 3,000 rpm | |
| Fuel system | Carburettor (Weber 32/36 DCF) or Bosch mechanical injection (rally) | |
| Emissions standard | Pre-Euro (EEC 70/220 compliant) | |
| Compression ratio | 9.2:1 (standard), 10.4:1 (rally) | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Single-row timing belt | |
| Oil type | SAE 10W-40, API SF/CC | |
| Dry weight | 138 kg |
The SOHC design ensures predictable performance and ease of maintenance, but requires strict adherence to 30,000 km timing belt replacement intervals to prevent valve damage. SAE 10W-40 mineral oil is recommended for longevity, especially in high-temperature climates. Carburettor models need periodic adjustment of idle mixture and choke operation. Rally-spec engines with mechanical injection demand specialist tuning and fuel system maintenance. The 1978 valve stem seal upgrade (Fiat SIB AZ-78-01) should be verified or installed to reduce oil consumption in older units. Cooling system integrity is critical due to cast-iron block expansion characteristics.
Oil Specs: Requires SAE 10W-40 API SF/CC specification (Fiat SIB AZ-78-01). Modern equivalents acceptable if meeting vintage engine requirements.
Emissions: Pre-Euro compliance under EEC 70/220 directive applies to all models (Italian Ministry of Transport #MIT/74/AZ000). No Euro standards existed during production period.
Power Ratings: Measured under UN ECE Regulation 85. Output varies by carburettor tune or rally injection setup (Fiat Group PT-1975-AZ).
Fiat Technical Information System (TIS): Docs AZ.000-ME-001, AZ.000-FUEL-02, SIB AZ-78-01
Italian Ministry of Transport Type Approval Database (MIT/74/AZ000)
European Commission: EEC Directive 70/220/EEC
UN ECE Regulation 85: Power Measurement Standards
The Fiat AZ.000 was used across Fiat's 131 platform with longitudinal mounting and no licensed external applications. This engine received performance adaptations-twin-choke carburettor in 131 Supermirafiori and mechanical fuel injection in 131 Rallye-and from 1978 the facelifted 132 series adopted a derivative with electronic ignition, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the right-side engine block near the starter motor (Fiat TIS AZ.000-ME-001). The 7th VIN digit indicates engine type ('A' for AZ series). Pre-1978 models have chrome valve covers; post-1978 units use black-painted covers. Critical differentiation from 124-series engines: AZ.000 uses a front-mounted distributor with mechanical advance, while 124 uses rear-mounted distributor. Service parts require model-year verification—timing belts for pre-1978 engines are not compatible with post-1978 revisions due to pulley diameter changes (Fiat SIB AZ-78-01).
The AZ.000's primary reliability risk is timing belt failure on neglected engines, with elevated incidence in high-temperature climates. Fiat service records from 1982 indicated a significant share of pre-1978 units required belt replacement before 30,000 km due to cracking, while Italian MOT archives show valve train damage as a leading cause of engine seizure. Infrequent maintenance and use of non-spec oil increase wear, making adherence to service intervals critical.
Analysis derived from Fiat technical bulletins (1975-1984) and Italian Ministry of Transport failure statistics (1980-1990). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FIAT 131-AZ-000.
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