The Fiat 138 AS.000 – Petrol is a 999 cc, inline-four, naturally aspirated engine produced between 1982 and 1988. It was developed as a compact, lightweight powerplant for Fiat's city and subcompact vehicles, featuring a single overhead camshaft (SOHC), 8-valve configuration, and carburetted fuel delivery. It produced 36 kW (49 PS) at 5,200 rpm and 71 Nm of torque at 3,000 rpm, providing adequate urban drivability with minimal complexity.
Fitted primarily to the Fiat Panda 30 and early Fiat Uno 45 models, the 138 AS.000 – Petrol was engineered for economical city commuting and low-cost ownership. Its driving character prioritized simplicity and fuel efficiency over performance, making it ideal for urban environments. Emissions compliance was managed through a basic catalytic converter and air injection system, allowing Euro 1 compliance in later production runs (1986–1988) per EU Directive 83/351/EEC.
One documented service update involved modifications to the cylinder head gasket design to address coolant leakage, referenced in Fiat Service Information Bulletin 85.07.03. Early batches exhibited higher-than-expected head gasket failure due to thermal cycling stress on the aluminium head. In 1985, Fiat introduced a revised multi-layer steel (MLS) gasket with improved sealing geometry, reducing field failures and improving long-term durability in warmer climates.
Production years 1982–1985 meet pre-Euro standards; 1986–1988 models comply with Euro 1 (EU Directive 83/351/EEC, VCA Type Approval #VCA/EM/887).
The Fiat 138 AS.000 – Petrol is a 999 cc inline-four SOHC engine engineered for city and subcompact applications (1982–1988). It combines carburetted fuel delivery with a compact iron-block design to deliver economical urban performance. Designed to meet early emissions standards (Euro 1), it prioritises simplicity, ease of maintenance, and low ownership costs.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 999 cc | |
| Fuel type | Petrol (Unleaded RON 95) | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 66.0 mm × 72.8 mm | |
| Power output | 36 kW (49 PS) @ 5,200 rpm | |
| Torque | 71 Nm @ 3,000 rpm | |
| Fuel system | Weber 30 HIC carburettor | |
| Emissions standard | Pre-Euro (1982–1985); Euro 1 (1986–1988) | |
| Compression ratio | 9.2:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven (SOHC, rear-mounted) | |
| Oil type | SAE 10W-40 (API SF/CC) | |
| Dry weight | 85 kg |
The carburetted SOHC design ensures simple operation and low repair costs, but requires periodic carburettor adjustment and choke calibration to maintain cold-start reliability. SAE 10W-40 mineral oil is sufficient, though semi-synthetic blends improve valve train longevity. The chain-driven timing system is durable but inaccessible without ancillary removal; inspection is recommended at 120,000 km intervals. Use of unleaded fuel mandates hardened valve seats—verified in post-1985 builds per Fiat SIB 85.07.03. The engine’s low torque output necessitates frequent downshifting in hilly terrain, and cooling efficiency declines if radiator scaling is neglected. Pre-1986 models lack catalytic converters and should not be retrofitted without ECU and exhaust modifications.
Oil Specs: Requires SAE 10W-40 (API SF/CC) specification (Fiat Owner's Manual 138.000.001). Compatible with modern API SM if seal compatibility verified.
Emissions: Euro 1 certification applies to 1986–1988 models only (VCA Type Approval #VCA/EM/887). Pre-1986 units comply with EU Directive 70/220/EEC.
Power Ratings: Measured under ECE R85 standards. Output varies with carburettor jetting and ambient temperature (Fiat TIS Doc. M102.005).
Fiat Technical Information System (TIS): Docs M102.001–M102.005, SIB 84.05.12, SIB 85.07.03
VCA Type Approval Database (VCA/EM/887)
European Commission: Directive 83/351/EEC
The Fiat 138 AS.000 – Petrol was used across Fiat's 141/146 platforms with transverse mounting and no licensing partnerships. This engine received platform-specific adaptations-shorter intake manifolds in the Uno and simplified ignition in the Panda-and from 1986 the Euro 1-compliant variants included catalytic converters and oxygen sensors, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front-facing side of the cylinder block, near the exhaust manifold (Fiat TIS M102.006). The 8th VIN digit indicates engine type ('B' for 138 AS.000). Pre-1986 models have chrome valve covers with exposed breather hoses; post-1986 units feature black plastic covers with integrated PCV. Critical differentiation from 100 Series: 138 AS.000 has a rear-mounted timing chain and carburettor; 100 Series engines use front belts and fuel injection. Service parts require model-year verification—head gaskets before 07/1985 are incompatible with MLS revisions per Fiat SIB 85.07.03.
The 138 AS.000 – Petrol's primary reliability risk is cylinder head gasket failure, with elevated incidence in high-temperature operation. Internal Fiat service data from 1985 reported over 15% of pre-1986 units requiring gasket replacement before 80,000 km, while VCA field reports correlate coolant loss with neglected thermostat maintenance. Extended idling and poor coolant flow increase thermal stress, making cooling system upkeep critical.
Analysis derived from Fiat technical bulletins (1983-1988) and UK VCA failure statistics (1985-1990). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FIAT 138-AS-000.
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