The Volvo B 6304 S is a 2,922 cc, inline‑six petrol engine produced between 1991 and 1998. It features a dual overhead camshaft (DOHC) design with 24 valves and multi‑point fuel injection. This naturally aspirated powerplant delivered outputs ranging from 170 to 204 PS, providing smooth, linear power delivery characteristic of Volvo's engineering philosophy.
Fitted primarily to the 960 sedan and wagon (including the 964 and 965 variants), the B 6304 S was engineered for…
Production years 1991–1995 meet Euro 1 standards; 1996–1998 models meet Euro 2 compliance depending on market (VCA UK Type Approval #VCA/EMS/VOLVO960).
The Volvo B 6304 S is a 2,922 cc inline‑six naturally aspirated petrol engine engineered for executive sedans and wagons (1991-1998). It combines DOHC 24-valve architecture with multi-point fuel injection to deliver smooth, linear power and quiet refinement. Designed to meet Euro 1 and Euro 2 standards, it prioritizes drivability and durability over outright performance.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,922 cc | |
Fuel type | Petrol | |
Configuration | Inline‑6, DOHC, 24‑valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 81.0 mm × 90.0 mm | |
Power output | 170–204 PS (125–150 kW) | |
Torque | 260–280 Nm @ 4,000–4,700 rpm | |
Fuel system | Bosch LH 2.4 or 3.2 multi-point injection | |
Emissions standard | Euro 1 (pre-1996); Euro 2 (1996-1998) | |
Compression ratio | 10.3:1 | |
Cooling system | Water‑cooled | |
Turbocharger | None | |
Timing system | Chain-driven | |
Oil type | SAE 10W-30 or 5W-30 (ACEA A3/B3) | |
Dry weight | 190 kg |
The Volvo B 6304 S was used exclusively across Volvo's 960 platform with longitudinal mounting. This engine received minor ECU and emissions revisions for the 1995 model year facelift, creating slight interchange limits for electronic components. All adaptations are documented in OEM technical bulletins.
The B 6304 S's primary reliability risk is electronic throttle module (ETM) failure, with elevated incidence in high-mileage vehicles. Volvo TSB TSB-001-1997 documents this as a prevalent service issue, while general owner reports frequently cite cooling system component wear after 200,000 km. Infrequent oil changes can accelerate timing chain tensioner wear, making adherence to service intervals critical.
Analysis derived from Volvo technical bulletins (1995-1998) and aggregated owner-reported failure data (1998-2023). Repair procedures should follow manufacturer guidelines.
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The B 6304 S is fundamentally robust, known for smooth operation and longevity when maintained. Key concerns are the ETM and cooling system components. With proactive replacement of the timing tensioner, water pump, and hoses, and addressing the ETM promptly, these engines can reliably exceed 300,000 km.
The most frequent issues are Electronic Throttle Module (ETM) failure causing idle problems, cooling system leaks from the water pump or hoses, and timing chain tensioner wear leading to rattling noises. Oil leaks from the valve cover are also common on high-mileage examples.
The B 6304 S engine was used exclusively in the Volvo 960 series, powering both the sedan (chassis code 964 pre-1995, 965 post-1995) and the estate/wagon (also 964/965) from model years 1991 through 1998. No other Volvo models used this specific engine variant.
Significant power gains are difficult. The engine is naturally aspirated and tuned for smoothness. Basic mods like a performance air filter or exhaust may yield minor gains (5-10 PS). Major power increases would require forced induction, which is complex and costly for this engine.
Fuel economy is moderate for its size and era. Expect approximately 11-13 L/100km (22-26 mpg UK) in combined city/highway driving for a sedan. Highway cruising can yield 8-9 L/100km (31-35 mpg UK). Actual figures vary greatly with driving style and vehicle condition.
Yes. The B 6304 S is an interference engine. If the timing chain fails or jumps significantly, the pistons will collide with the open valves, causing catastrophic internal engine damage. This underscores the importance of maintaining the timing chain system.
Volvo recommends a high-quality 10W-30 or 5W-30 mineral or semi-synthetic oil meeting ACEA A3/B3 specifications. Full synthetic 5W-30 is also suitable and may offer better protection, especially in colder climates or for extended service intervals.
Comprehensive technical documentation and regulatory references
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UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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GOV.UK: Vehicle Approval
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