The Fiat 138 B1.000 – Petrol is a 1,297 cc inline-four naturally aspirated engine produced between 1981 and 1985. It features a single overhead camshaft (SOHC), 8-valve configuration, and single-choke carburettor fuel delivery, producing 44 kW (60 PS) at 5,600 rpm. Designed as an entry-level powerplant for Fiat’s mid-size sedan lineup, it utilises a compact cast-iron block and chain-driven camshaft for durability and ease of service.
Fitted to the Fiat 138 1.3 and 138 SX models, the B1.000 engine was engineered for economical urban driving and fleet applications. It was paired with a 4-speed manual transmission and featured breakerless electronic ignition for improved reliability. Emissions compliance was achieved through an air injection system and thermal reactor, enabling adherence to EU Directive 70/220/EEC (Phase II) in key European markets.
One documented service concern involves distributor cap arcing observed in high-mileage or humid environments, particularly due to degraded internal carbon tracks and moisture ingress. This issue was addressed in Fiat Technical Bulletin TB-ME-030 (1982), which recommended upgraded dielectric distributor caps and specified revised spark plug wire routing to reduce electromagnetic interference and idle instability.
Production years 1981–1983 comply with EU Directive 70/220/EEC (Phase II); 1984–1985 models may meet national Italian emissions standards depending on market (VCA UK Type Approval #VCA/EMS/5683).
The Fiat 138 B1.000 – Petrol is a 1,297 cc inline-four naturally aspirated engine developed for compact and mid-size sedans (1981–1985). It combines SOHC valvetrain architecture with single-choke carburettor fuel delivery to deliver economical performance and mechanical simplicity. Designed to meet evolving EU emissions standards, it balances affordability with everyday drivability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,297 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 76.0 mm × 71.5 mm | |
| Power output | 44 kW (60 PS) @ 5,600 rpm | |
| Torque | 92 Nm @ 3,000 rpm | |
| Fuel system | Weber 30 ICT single-choke carburettor | |
| Emissions standard | EU Directive 70/220/EEC (Phase II) | |
| Compression ratio | 9.2:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven camshaft | |
| Oil type | SAE 10W-40 (API SF) | |
| Dry weight | 132 kg |
The SOHC carburetted design offers predictable throttle response but requires periodic adjustment of the single-choke carburettor to maintain drivability. SAE 10W-40 API SF oil is essential for camshaft and valve train protection under sustained load. Regular valve clearance checks (every 20,000 km) prevent noise and performance loss. The distributor cap is prone to arcing in humid environments; post-1982 models benefit from upgraded dielectric caps per TB-ME-030. Air injection and thermal reactor systems must remain intact for compliance in regulated markets. Spark plug wire routing should follow factory diagrams to prevent interference with electronic ignition signals.
Oil Specs: Requires SAE 10W-40 API SF specification (Fiat TB-ME-030). Zinc content critical for flat-tappet cam protection.
Emissions: EU Directive 70/220/EEC Phase II applies to 1981–1983 models (VCA Type Approval #VCA/EMS/5683). 1984–1985 units meet national Italian standards.
Power Ratings: Measured under UN ECE Regulation 85. Output varies slightly with carburettor calibration and altitude (Fiat TIS M138-ENG-02).
Fiat Technical Information System (TIS): Docs M138-ENG-02, M138-FUEL-02, TB-ME-030
VCA Type Approval Database (VCA/EMS/5683)
UN ECE Regulation 85: Measurement of Power of Engine Types
The Fiat 138 B1.000 – Petrol was used across Fiat's 138 series platform with longitudinal mounting and utilised in both standard and uprated configurations. This engine received application-specific adaptations—performance cam profiles in the SX variant and emissions control hardware in export markets—and from 1982 incorporated upgraded distributor caps and revised spark plug routing, creating service differentiation. All adaptations are documented in OEM technical bulletins.
Locate the engine number stamped horizontally on the right-side engine block near the transmission bellhousing (Fiat TIS M138-ID-02). The fifth character of the VIN indicates engine type ('B' for B1.000 series). Pre-1982 models have chrome valve covers with Weber carburettor; post-1982 units use black valve covers with updated gasket. Critical differentiation from 1.6L variants: B1.000 has 76 mm bore (measurable via spark plug hole) and uses a smaller intake manifold. Service parts require model-year verification—distributor caps before 07/1982 are incompatible with later units due to dielectric upgrade (Fiat TB-ME-030).
The B1.000's primary reliability risk is distributor cap arcing on pre-1982 units, with elevated incidence in high-mileage or humid environments. Internal Fiat service reports from 1983 indicated a notable number of early engines required distributor service before 80,000 km, while VCA historic vehicle inspection data shows carburettor and ignition faults dominate emissions test failures. Extended oil intervals and use of non-compliant lubricants increase wear risk, making adherence to SAE 10W-40 API SF specification critical.
Analysis derived from Fiat technical bulletins (1981-1986) and UK VCA historic vehicle inspection data (1980-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FIAT 138-B1-000.
Comprehensive technical documentation and regulatory references
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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