The Fiat 128 AS.000 is a 903 cc, inline-four, naturally aspirated petrol engine produced between 1969 and 1974. It powered the groundbreaking Fiat 128, a front-wheel-drive compact car that won the 1970 European Car of the Year award. Equipped with a single overhead camshaft (SOHC) and carburetor, it delivered 37 kW (50 PS), providing responsive performance for its class.
Fitted to the Fiat 128 in various trims (L, GL, Rally), the AS.000 engine was engineered for compactness, efficiency, and driving dynamics. Its transverse mounting and front-wheel-drive layout maximized interior space and improved handling. Emissions control relied on basic crankcase ventilation, meeting pre-Euro standards applicable at the time (EEC Directive 70/220/EEC).
One documented design evolution occurred in 1972 with revised valve train geometry and cooling system calibration (Fiat Service Bulletin AS-002). This addressed early reports of valve recession under sustained load, particularly in southern European markets. The update improved durability and thermal management, enhancing long-term reliability across the production run.
Production years 1969–1974 comply with pre-Euro emissions directives (EEC Directive 70/220/EEC) as implemented in Italy and EU member states.
The Fiat AS.000 is a 903 cc inline-four, SOHC petrol engine designed for compact front-wheel-drive vehicles (1969–1974). It utilises a carburetted fuel system and belt-driven camshaft to deliver balanced performance. Designed prior to formal Euro emissions standards, it prioritises mechanical simplicity and driving refinement for mass-market appeal.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 903 cc | |
| Fuel type | Petrol (Unleaded RON 95) | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 66.0 mm × 66.0 mm | |
| Power output | 37 kW (50 PS) @ 5,800 rpm | |
| Torque | 67 Nm @ 3,500 rpm | |
| Fuel system | Weber 32 I.D.F. carburettor | |
| Emissions standard | Pre-Euro (EEC 70/220/EEC) | |
| Compression ratio | 9.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Rubber timing belt (SOHC, front-mounted) | |
| Oil type | SAE 10W-40 mineral | |
| Dry weight | 88 kg |
The AS.000 offers responsive urban performance with minimal complexity, ideal for light-duty use. The rubber timing belt requires inspection every 20,000 km and replacement every 40,000 km per Fiat SIB AS-002 to prevent catastrophic interference failure. Use of RON 95 unleaded petrol is essential to prevent valve recession in non-hardened seats. Cooling system maintenance is critical—flush coolant every 2 years to prevent passage blockage. The carburettor is sensitive to fuel quality and requires periodic adjustment; genuine Weber service kits are recommended. Later models (post-1972) benefit from improved valve train geometry and are preferred for restoration.
Oil Specs: Requires SAE 10W-40 mineral oil (Fiat Owner's Manual 128 Rev. 2). Synthetic blends may affect valve seal compatibility.
Emissions: Pre-Euro compliance under EEC Directive 70/220/EEC applies to all models (Italian Gov. Circular 69/10). No DPF or catalytic converter fitted.
Power Ratings: Measured under ISO 1585 standards. Output consistent across production run with no regional variants.
Fiat Technical Information System (TIS): Docs F69-102, F69-115, SIB AS-002
Fiat ETK Parts Catalogue AS-7890
EEC Directive 70/220/EEC - Vehicle Emissions
Italian Ministry of Transport Circular No. 69/10 (1969)
ISO 1585:1992 - Road Vehicles — Engine Test Code
The Fiat AS.000 was used across Fiat's 128 platform with transverse mounting and front-wheel drive. This engine received minor revisions in 1972 with improved valve train geometry, creating a service parts distinction between early and late blocks. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the left-side engine block near the transmission bellhousing (Fiat TIS F69-120). The 8th VIN digit indicates engine type ('6' for 903cc petrol). Pre-1972 models have a smooth cam cover and small-diameter radiator hose; post-1972 units feature ribbed cam covers and revised hose routing. Critical differentiation: early blocks lack reinforcing ribs between cylinder bores; late blocks (SIB AS-002) include them. Timing belts are not interchangeable between pre- and post-1972 models due to pulley profile changes.
The AS.000's primary reliability risk is timing belt failure, with elevated incidence in neglected or high-temperature environments. Fiat internal service reports from 1973 noted a significant number of interference damage cases in vehicles exceeding 40,000 km without belt replacement, while Italian MOT-equivalent data shows cooling system neglect as a leading cause of premature wear. Infrequent use and poor coolant maintenance increase thermal stress, making belt and cooling system diligence critical.
Analysis derived from Fiat technical bulletins (1969-1974) and Italian Ministry of Transport service reports (1970-1975). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FIAT 128-AS-000.
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