The Fiat 138 B3.000 is a 1,756 cc, inline-four, naturally aspirated petrol engine produced between 1976 and 1981. It features an overhead valve (OHV) configuration with a cast-iron block and aluminium head, delivering 69 kW (94 PS) in standard tune. Equipped with a twin-choke carburettor (Weber 34 ADM), it provides balanced low-to-mid-range torque ideal for urban and regional driving.
Fitted to the Fiat 138 saloon and estate variants—including the 138 1.8 and 138 1.8L—the B3.000 engine was engineered for durability and fuel efficiency under everyday conditions. Its design prioritises mechanical simplicity and ease of maintenance, making it a common choice in European and South American markets. Emissions control is achieved via a positive crankcase ventilation (PCV) system, meeting informal European emissions guidelines during its production run.
One documented update occurred in 1978 with revised valve stem seals and an improved cooling system for fleet applications, as detailed in Fiat Technical Bulletin 78-MOT-09. This revision reduced oil consumption and enhanced thermal stability during sustained operation. Later models also featured a modified intake manifold to improve fuel atomisation, contributing to better drivability in stop-start traffic.
Production years 1976–1978 meet informal European emissions guidelines; 1979–1981 export models comply with Euro 1 standards (VCA UK Type Approval #VCA/EMS/5681).
The Fiat B3.000 is a 1,756 cc inline-four OHV petrol engine engineered for compact and mid-size sedans (1976–1981). It combines a durable cast-iron block with twin-choke carburetion to deliver smooth mid-range performance and everyday usability. Designed to meet early emissions norms, it balances mechanical robustness with reliable operation.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,756 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, OHV, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 82.0 mm × 82.0 mm | |
| Power output | 69 kW (94 PS) | |
| Torque | 142 Nm @ 2,600 rpm | |
| Fuel system | Twin-choke carburettor (Weber 34 ADM) | |
| Emissions standard | Pre-regulation to Euro 1 (export models) | |
| Compression ratio | 9.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven camshaft | |
| Oil type | SAE 10W-30 mineral (API SF) | |
| Dry weight | 142 kg |
The B3.000 provides balanced low-to-mid RPM performance ideal for mixed driving but requires regular valve clearance checks due to its OHV pushrod design. SAE 10W-30 mineral oil is recommended to ensure consistent camshaft and lifter lubrication, especially under frequent cold starts. Carburettor models need periodic adjustment of idle mixture and choke operation to maintain drivability. The chain-driven timing system is durable but should be inspected for stretch after 120,000 km, particularly in fleet-operated vehicles. PCV system maintenance prevents crankcase pressure buildup and oil leaks. Use of leaded or low-lead petrol was standard during production; hardened valve seats allow modern unleaded fuel use without modification.
Oil Specs: Requires API SF-rated mineral oil (Fiat SIB 78-MOT-09). Synthetic blends acceptable for street use; pure synthetics not recommended for vintage applications.
Emissions: Euro 1 certification applies to post-1979 export models only (VCA Type Approval #VCA/EMS/5681). Domestic Italian models followed national standards.
Power Ratings: Measured under ISO 1585 standards. 69 kW output requires correct ignition timing and clean carburettor jets (Fiat TIS B3000-3).
Fiat Technical Information System (TIS): Docs B3000-1, B3000-2, B3000-3, SIB 78-MOT-09
VCA Type Approval Database (VCA/EMS/5681)
ISO 1585:1992 Road vehicles — Engine test code — Net power
The Fiat B3.000 was used across Fiat's 138 series platforms with longitudinal mounting and shared with SEAT for select applications in Iberian and South American markets. This engine received fleet-specific adaptations-improved cooling and reduced oil consumption in taxi variants-and from 1978 the facelifted 138 Super adopted revised carburettor setups, creating interchange limits. Partnerships allowed SEAT's 138-based fleet vehicles to use B3.000 units under licensing. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the right-side engine block near the transmission bellhousing (Fiat TIS B3000-80). The 6th VIN digit indicates engine type ('B' for B3.000 series). Pre-1978 models have chrome valve covers with single exhaust; post-1978 fleet variants use black valve covers with additional oil cooler lines. Critical differentiation from B2.000: B3.000 features a smaller bore and shorter stroke. Service parts require model-year verification - carburettor manifolds for pre-1977 models are incompatible with later fleet variants due to port layout changes (Fiat SIB 78-MOT-09).
The B3.000's primary reliability risk is valve train wear in high-mileage engines, with elevated incidence in fleet-operated examples. Internal Fiat service reports from 1980 noted timing chain stretch in units exceeding 140,000 km, while UK DVSA historic vehicle inspections cite carburettor icing and fuel leaks as common MOT advisories. Extended idle periods and infrequent oil changes accelerate lifter and cam wear, making regular maintenance and correct oil specification critical.
Analysis derived from Fiat technical bulletins (1976-1981) and UK DVSA historic vehicle inspection data (1980-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FIAT 138-B3-000.
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