The Volvo B6304S3 is a 2,922 cc, inline‑six petrol engine produced between 1995 and 1998. It features a dual overhead camshaft (DOHC) design with four valves per cylinder and Bosch LH‑Jetronic 3.2 fuel injection. This naturally aspirated powerplant delivered 170 kW (230 PS) and 294 Nm of torque, providing smooth, linear power delivery characteristic of Volvo’s straight‑six engines.
Fitted primarily to the 850 R and early S/V70 R models, the B6304S3 was engineered for sp…
Production years 1995–1998 meet Euro 2 standards (VCA UK Type Approval #VCA/EMS/5678).
The Volvo B6304S3 is a 2,922 cc inline‑six naturally aspirated petrol engine engineered for premium performance sedans and wagons (1995-1998). It combines DOHC valvetrain with Bosch LH-Jetronic fuel injection to deliver smooth, linear power and high-revving character. Designed to meet Euro 2 standards, it prioritizes drivability and mechanical refinement.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,922 cc | |
Fuel type | Petrol (Gasoline) | |
Configuration | Inline-6, DOHC, 24-valve | |
Aspiration | Naturally Aspirated | |
Bore × stroke | 81.0 mm × 90.0 mm | |
Power output | 170 kW (230 PS) @ 6,000 rpm | |
Torque | 294 Nm @ 4,200 rpm | |
Fuel system | Bosch LH-Jetronic 3.2 | |
Emissions standard | Euro 2 | |
Compression ratio | 10.3:1 | |
Cooling system | Water-cooled | |
Turbocharger | None | |
Timing system | Chain-driven | |
Oil type | SAE 10W-30 (API SH/CD) | |
Dry weight | 187 kg |
The Volvo B6304S3 was used exclusively in Volvo's high-performance 850 platform with longitudinal mounting. This engine received specific adaptations-reinforced engine mounts and a unique exhaust manifold-for the 850 R model. From 1997, the S/V70 R models adopted the B6304S3 before its discontinuation. All adaptations are documented in OEM technical bulletins.
The B6304S3's primary reliability risk is ignition system failure, specifically the distributor cap and rotor. Volvo TSB-12-96 documents a high incidence of wear leading to misfires before 80,000 km in some vehicles. Extended service intervals and exposure to high under-hood temperatures accelerate this wear, making adherence to the 60,000 km replacement interval critical.
Analysis derived from Volvo technical bulletins (1995-1998) and UK DVSA failure statistics (1998-2010). Repair procedures should follow manufacturer guidelines.
The most common questions about engine codes, what they mean, how to find them and how this database works
The B6304S3 is a robust engine with a strong bottom end. Its main weakness is the distributor-based ignition system, which requires proactive replacement of the cap and rotor. With regular maintenance, especially timely oil changes and addressing cooling system components, it can be very reliable and last well beyond 300,000 km.
The most frequent issues are distributor cap/rotor failure causing misfires, oil leaks from the rear main seal, coolant leaks from aging plastic components, and broken exhaust manifold studs. These are well-documented in Volvo service bulletins from the mid-to-late 1990s.
The B6304S3 was used in the high-performance variants: the 850 R (1995-1996) and the S70 R / V70 R (1997-1998). It was the top-tier naturally aspirated six-cylinder engine for these models before being replaced by VVT-equipped engines.
Yes, but gains are modest due to its naturally aspirated design. Common modifications include a performance exhaust, intake, and ECU remap, which might yield 10-15 kW. Significant power increases require forced induction, which is complex and costly. Its strength is smooth, reliable power delivery.
Fuel economy is moderate for its era and performance. Expect around 12.5 L/100km (22.5 mpg UK) in city driving and 8.5 L/100km (33 mpg UK) on the highway for an 850 R. Real-world combined figures typically range from 25-28 mpg UK, heavily influenced by driving style.
Yes. The B6304S3 is an interference engine. If the timing chain fails (though rare) or jumps timing, the pistons will collide with the open valves, causing catastrophic internal engine damage. Regular oil changes help ensure chain longevity.
Volvo originally specified SAE 10W-30 oil meeting API SH/CD standards. A high-quality 10W-40 semi-synthetic or full synthetic oil is also suitable for modern use and may offer better high-temperature protection, especially for the timing chain and rear main seal.
Comprehensive technical documentation and regulatory references
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Regulation (EC) No 715/2007
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