The Fiat 138 B6.000 – Petrol is a 1,585 cc inline-four, overhead-valve (OHV) engine produced between 1983 and 1985. It served as the base petrol powerplant for the Fiat 138 sedan, delivering 59 kW (80 PS) at 5,600 rpm and 124 Nm of torque at 3,000 rpm. Equipped with a single downdraft carburettor and mechanical ignition, it prioritised simplicity and durability for economical family transport.
Fitted to the Fiat 138 1.6L across European markets, this engine was engineered for balanced fuel economy and drivability in a rear-wheel-drive executive sedan. Driving character emphasized predictable throttle response and ease of maintenance, making it suitable for urban commuting and regional travel. Emissions compliance was achieved through positive crankcase ventilation (PCV) and an air injection system, meeting Euro 0 (Phase II) standards.
One documented service update involves the cylinder head gasket material, addressed in Fiat Service Bulletin 84-09-06. Early builds used asbestos-based gaskets prone to degradation under sustained thermal load, leading to coolant leakage and head warping. From 1984 onward, Fiat introduced reinforced composite gaskets with improved sealing integrity, reducing failure rates and enhancing long-term reliability.
Production years 1983–1983 meet Euro 0 Phase I; 1984–1985 models comply with Phase II revisions (VCA UK Type Approval #VCA/E/7967).
The Fiat 138 B6.000 – Petrol is a 1,585 cc inline-four OHV engine engineered for executive sedan applications (1983–1985). It combines a carburetted fuel system with mechanical ignition to deliver reliable performance and ease of service. Designed to meet evolving European emissions standards, it balances durability with economy for high-mileage use.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,585 cc | |
| Fuel type | Petrol (Unleaded RON 95) | |
| Configuration | Inline-4, OHV, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 78.0 mm × 82.0 mm | |
| Power output | 59 kW (80 PS) @ 5,600 rpm | |
| Torque | 124 Nm @ 3,000 rpm | |
| Fuel system | Weber 32 I.D.F. carburettor | |
| Emissions standard | Euro 0 (Phase I pre-1984); Phase II (post-1984) | |
| Compression ratio | 9.0:1 | |
| Cooling system | Water-cooled, belt-driven pump | |
| Ignition system | Mechanical distributor with contact breaker | |
| Timing system | Chain-driven camshaft | |
| Oil type | SAE 10W-40 (API SF/CC) | |
| Dry weight | 139 kg |
The OHV design ensures predictable performance and ease of maintenance but requires valve clearance checks every 15,000 km to maintain efficiency. SAE 10W-40 mineral oil is recommended due to the flat-tappet camshaft's lubrication demands. Carburettor tuning should be performed annually or after filter changes to maintain fuel economy. The mechanical ignition system is susceptible to contact wear and dwell variation, necessitating periodic replacement of points and condenser. From 1984, revised composite head gaskets reduced failure rates; pre-1984 engines should be inspected for warping. PCV and air injection systems require inspection to prevent flow restrictions and oil contamination.
Oil Specs: Requires API SF/CC-rated 10W-40 (Fiat SIB 83-08-16). Zinc dialkyl dithiophosphate (ZDDP) content critical for cam lobe protection.
Emissions: Euro 0 Phase I applies to 1983 models (VCA Type Approval #VCA/E/7967). Phase II compliance from 1984 includes revised air injection routing.
Power Ratings: Measured under ISO 1585 standards. Output assumes clean air filter, correct ignition timing, and fresh fuel (Fiat TIS B6.000-TEST-03).
Fiat Technical Information System (TIS): Docs B6.000-TECH-01, B6.000-TEST-03, SIB 83-08-16, SIB 84-09-06
VCA Type Approval Database (VCA/E/7967)
ISO 1585:1996 Road Vehicles — Engine Test Code — Net Power
The Fiat 138 B6.000 – Petrol was used exclusively across Fiat's 138 platform with longitudinal mounting and no licensed external usage. This engine received platform-specific adaptations—fuel mixture calibration for high-altitude variants in Switzerland and Austria—and from 1984 the facelifted 138 SLX models adopted revised ignition timing curves, creating minor tune differences. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front face of the cylinder block, just below the exhaust manifold (Fiat TIS B6.000-ID-01). The 7th VIN digit indicates engine type ('B' for 1.6L petrol). Pre-1984 models have chrome valve covers with paper gaskets; post-1984 units use black enamel covers with rubber seals. Critical differentiation from 2.0L variants: B6.000 has a 32 I.D.F. Weber carburettor and smaller intake manifold. Service parts require model-year verification — head gaskets before 1984 are not interchangeable with post-1984 composite versions (Fiat SIB 84-09-06).
The B6.000 – Petrol's primary reliability risk is cylinder head gasket degradation in early builds, with elevated incidence in high-load or poorly cooled applications. Internal Fiat quality reports from 1983 indicated a notable share of pre-1984 engines required gasket replacement before 80,000 km, while VCA field data links overheating events to warped cylinder heads in neglected examples. Infrequent maintenance and extended oil change intervals increase thermal stress, making cooling system checks and timely gasket replacement critical.
Analysis derived from Fiat technical bulletins (1983–1985) and UK DVSA failure statistics (1980–1990). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FIAT 138-B6-000.
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