The Fiat 149 B4.000 is a 1,297 cc, inline-four, naturally aspirated petrol engine produced between 1983 and 1989. It belongs to Fiat's 149 series engine family, designed for compact and subcompact vehicles requiring improved performance over smaller units. Featuring a single overhead camshaft (SOHC), 8-valve configuration, and carburettor fuel delivery, it produces 51 kW (69 PS) at 5,600 rpm and 102 Nm of torque, offering enhanced drivability in urban and light-load applications.
Fitted primarily to the Fiat Regata 75 and later iterations of the Fiat Ritmo, the 149 B4.000 was engineered to balance fuel economy with increased torque for improved highway performance. It utilises a Weber 32/34 DFT twin-choke carburettor and a conventional distributor-based ignition system. Emissions control is achieved through an air injection system and catalytic converter on Euro 1-compliant models, meeting early European standards in select markets from 1986 onward.
One documented concern is intake manifold cracking near the thermostat housing, particularly under thermal cycling and improper coolant maintenance. This issue, referenced in Fiat Service Information Bulletin 84/07, can lead to coolant leaks and overheating. Later production revisions (post-1986) introduced a redesigned manifold with reinforced mounting bosses and improved material integrity to mitigate failure rates.
Production years 1983–1985 meet pre-Euro emissions benchmarks; 1986–1989 models with catalytic converters comply with early Euro 1 standards (VCA UK Type Approval #VCA/EMS/5679).
The Fiat 149 B4.000 is a 1,297 cc inline-four, SOHC petrol engine engineered for compact sedans and hatchbacks (1983–1989). It combines a carburetted fuel system with a cast-iron block and alloy head to deliver improved torque for everyday driving. Designed to meet early emissions standards, it balances mechanical simplicity with enhanced performance over smaller 1.0L variants.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,297 cc | |
| Fuel type | Petrol (Unleaded RON 95) | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 73.0 mm × 76.8 mm | |
| Power output | 51 kW (69 PS) @ 5,600 rpm | |
| Torque | 102 Nm @ 3,000 rpm | |
| Fuel system | Weber 32/34 DFT carburettor | |
| Emissions standard | Pre-Euro / Euro 1 (catalyst models) | |
| Compression ratio | 9.4:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven (single-row, non-adjustable) | |
| Oil type | SAE 10W-40, API SF | |
| Dry weight | 104 kg |
The naturally aspirated design provides linear throttle response ideal for city driving but requires regular carburettor servicing to maintain efficiency. SAE 10W-40 mineral oil meeting API SF standards is recommended with 12,000 km service intervals to ensure timing chain and camshaft lubrication. The Weber 32/34 DFT carburettor is sensitive to fuel quality and should be inspected or rebuilt every 40,000 km. Intake manifold cracking is documented in Fiat SIB 84/07, particularly in engines with neglected coolant changes. Post-1986 models feature reinforced manifolds for improved durability. Emissions-controlled variants require functional air injection and catalytic converters to remain compliant in regulated markets.
Oil Specs: Requires API SF-rated 10W-40 oil (Fiat SIB 84/07). No BMW Longlife or ACEA specifications apply.
Emissions: Euro 1 certification applies to catalyst-equipped models from 1986 only (VCA Type Approval #VCA/EMS/5679). Pre-1986 units are pre-regulatory.
Power Ratings: Measured under ISO 1585 standards. Output varies with carburettor calibration and ambient conditions (Fiat TIS Doc. A14909).
Fiat Technical Information System (TIS): Docs A14906, A14907, A14908, SIB 84/07
VCA Type Approval Database (VCA/EMS/5679)
ISO 1585:1996 Road vehicles — Test method for the measurement of fuel consumption
The Fiat 149 B4.000 – Petrol was used across Fiat's 138 and 146 platforms with transverse mounting and no licensed external applications. This engine received platform-specific adaptations-revised intake manifolds in the Regata and modified exhaust routing in the Ritmo-and from 1986 the facelifted Regata 75 SL models adopted a catalytic converter and lambda sensor, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front face of the cylinder block, near the timing cover (Fiat TIS A14911). The 8th VIN digit indicates engine type ('B' for 149 series). Pre-1986 models have chrome valve covers with side-mounted oil filler; post-1986 units use black plastic covers. Critical differentiation from 149 A3.000: 149 B4.000 uses a larger bore (73.0 mm vs 66.0 mm), Weber 32/34 DFT carburettor, and distinct intake manifold. Service parts require model-year verification—catalyst-equipped variants (1986+) are not compatible with pre-cat exhaust manifolds (Fiat SIB 86/08).
The 149 B4.000's primary reliability risk is intake manifold cracking on early builds, with elevated incidence in vehicles with irregular coolant changes. Internal Fiat quality reports from 1985 noted a significant number of pre-1986 engines requiring manifold replacement before 90,000 km, while VCA field data indicates carburettor-related failures dominate emissions test failures in urban fleets. Extended oil intervals and poor fuel quality accelerate wear and mixture imbalance, making maintenance adherence and cooling system care critical.
Analysis derived from Fiat technical bulletins (1983-1989) and UK VCA failure statistics (1985-1990). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FIAT 149-B4-000.
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