The Fiat 138 AR2.000 is a 1,995 cc, inline-four, naturally aspirated petrol engine produced between 1982 and 1988. It was developed as part of Fiat's Tipo Quattro engine family, featuring a cast-iron block, aluminium head, and belt-driven SOHC valvetrain. Delivering 86–90 kW (117–122 PS) depending on application, it offered a balance of durability and mid-range performance for executive sedans and coupes.
Fitted primarily to the Lancia Beta Montecarlo Turbo (Type 138) and select Fiat 131 models, the 138 AR2.000 was engineered for spirited driving and highway stability. Its design prioritised mechanical simplicity and serviceability, with emissions compliance achieved through early-generation lambda-controlled fuel injection and catalytic converter systems, allowing it to meet initial Euro 1 precursor standards in certain export markets.
One documented concern is cylinder head warping under sustained high load, particularly in turbocharged applications. This issue, noted in Fiat Technical Service Bulletin 85/04, is linked to inadequate coolant flow in modified or poorly maintained units. Later revisions included upgraded head bolts and revised cooling system routing to improve thermal management.
Production years 1982–1988 meet pre-Euro emissions standards; export variants comply with UNECE Regulation 15/04 (VCA UK Type Approval #VCA/ECE/82-04).
The Fiat 138 AR2.000 is a 1,995 cc inline-four petrol engine engineered for performance coupes and sedans (1982–1988). It combines SOHC 8-valve architecture with Bosch K-Jetronic or L-Jetronic fuel injection to deliver linear power delivery and mechanical robustness. Designed to meet early emissions protocols, it balances driver engagement with serviceability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,995 cc | |
| Fuel type | Petrol (Unleaded RON 95) | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 87.0 mm × 84.0 mm | |
| Power output | 86–90 kW (117–122 PS) @ 5,200–5,600 rpm | |
| Torque | 160–168 Nm @ 3,000–3,500 rpm | |
| Fuel system | Bosch K-Jetronic (mechanical) or L-Jetronic (electronic) | |
| Emissions standard | Pre-Euro / UNECE Reg 15/04 | |
| Compression ratio | 9.2:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Single-row timing belt | |
| Oil type | SAE 10W-40, API SF/CC | |
| Dry weight | 138 kg |
The naturally aspirated design provides predictable throttle response ideal for spirited driving but requires strict adherence to 30,000 km timing belt replacement intervals to prevent valve damage. SAE 10W-40 mineral or semi-synthetic oil meeting API SF/CC is recommended for optimal camshaft and lifter lubrication. Extended idling or high-load operation without proper warm-up increases cylinder head thermal stress. Bosch L-Jetronic systems require periodic airflow meter calibration to maintain fuel trim accuracy. Units with modified exhaust or intake should have fueling reviewed per Fiat SIB 87/12 to prevent lean conditions. Cooling system integrity is critical—leaks or air pockets can accelerate head warping in high-temperature operation.
Oil Specs: Requires SAE 10W-40 API SF/CC specification (Fiat SIB 85/04). Compatible with modern API SM/CF oils if SF-rated.
Emissions: Pre-Euro compliance applies to all models (VCA Type Approval #VCA/ECE/82-04). Export variants meet UNECE Regulation 15/04.
Power Ratings: Measured under ISO 1585 standards. Output varies by carburetion/fuel injection type (Fiat Group PT-1983).
Fiat Technical Information System (TIS): Docs A138-400, SIB 85/04, SIB 87/12
VCA Type Approval Database (VCA/ECE/82-04)
ISO 1585: Road vehicles — Engine test code — Net power
The Fiat 138 AR2.000 was used across Fiat's 131 and Lancia's Montecarlo platforms with longitudinal mounting and shared architecture with Lancia performance variants. This engine received platform-specific adaptations-fuel injection tuning in the Montecarlo and carburetted variants in the 131 Rally-and from 1985 the facelifted Montecarlo Turbo models adopted revised intake manifolds, 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 starter motor (Fiat TIS A138-410). The 8th VIN digit indicates engine type ('G' for 2.0L AR-series). Pre-1984 units have chrome valve covers with carburettors or K-Jetronic; post-1984 Turbo models feature black valve covers with turbo manifolds. Critical differentiation from 1.8L AR1800: 138 AR2.000 has larger bore (87.0 mm vs 84.0 mm) and distinct intake manifold. Service parts require model-year verification—timing belts for pre-1985 models are not compatible with later Turbo variants due to pulley redesign (Fiat SIB 86/09).
The 138 AR2.000's primary reliability risk is cylinder head warping, with elevated incidence in turbocharged or modified applications. Internal Fiat engineering reports from 1986 indicated a significant number of Montecarlo Turbo units required head resurfacing before 80,000 km, while UK DVSA historic vehicle records show timing belt neglect as a leading cause of engine failure in preserved models. High-temperature operation and infrequent maintenance increase thermal stress, making cooling system checks and belt replacement critical.
Analysis derived from Fiat technical bulletins (1983-1988) and UK DVSA historic vehicle inspection data (1980-1995). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FIAT 138-AR-2000.
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