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 spirited performance combined with everyday refinement and durability. Emissions compliance for its era was managed through a three‑way catalytic converter and electronic engine management, meeting Euro 2 standards.
One documented service concern is premature wear of the distributor cap and rotor, which can lead to misfires and rough running. This issue, addressed in Volvo Technical Service Bulletin TSB‑12‑96, is attributed to heat stress within the distributor housing. The B6304S3 was superseded by the B6254S and B6294S engines with VVT technology.
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 naturally aspirated inline-six provides a smooth, linear power band ideal for highway cruising but requires premium unleaded fuel (RON 95+) for optimal performance and to prevent knocking. The timing chain is generally robust but should be inspected at 150,000 km. The Bosch LH-Jetronic system is reliable but sensitive to poor electrical grounds; distributor cap and rotor should be replaced every 60,000 km to prevent misfires per TSB-12-96. Engine mounts on the 850 R are performance-oriented and may wear faster than standard models.
Oil Specs: Requires SAE 10W-30 meeting API SH/CD specification (Volvo Owner's Manual 850R).
Emissions: Euro 2 certification applies to all 1995-1998 models (VCA Type Approval #VCA/EMS/5678).
Power Ratings: Measured under DIN 70020 standards. Output requires 95 RON fuel (Volvo TDS-6304).
Volvo Technical Information System: Docs TP 30780, TDS-6304, TSB-12-96
VCA Type Approval Database (VCA/EMS/5678)
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.
Locate the engine code stamped on the left side of the cylinder block, just below the exhaust manifold (Volvo Service Manual TP 30780). The 8th VIN digit for B6304S3-equipped 850 R models is '5', and for S/V70 R models, it is '7'. The engine is visually identified by its red valve cover and the "2.9 24V" badge on the front. Critical differentiation from the B6254: The B6304S3 has a larger displacement (2.9L vs 2.5L) and a unique intake plenum. Distributor-based ignition is a key identifier against later coil-on-plug B6xxx engines.
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.
Find answers to most commonly asked questions about VOLVO B-6304-S3.
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