The BMW M30 B30 (306KA) is a 2,986 cc, inline — six naturally aspirated petrol engine produced from 1971 to 1982. Part of BMW's long — running M30 engine family, it features a cast — iron block, aluminum head, and SOHC 12 — valve configuration with belt — driven camshaft. Delivering 135 kW (184 PS) and 275 Nm of torque at 3,800 rpm, this engine was engineered for smooth performance and relaxed cruising in executive sedans.
Installed in the E3 3.0 CS coupes and E24 6 Series, the M30 B3…
All production years 1971–1982 meet applicable pre-Euro emissions standards .
The BMW M30 B30 (306KA) is a 2,986 cc inline-six naturally aspirated petrol engine engineered for grand tourers (1971–1982). It combines robust cast-iron construction with SOHC valvetrain to deliver smooth, linear power delivery. Designed to meet pre-Euro emissions standards, it balances mechanical simplicity with driving refinement.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,986 cc | |
Fuel type | Petrol | |
Configuration | Inline-6, SOHC, 12-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 89.0 mm × 80.0 mm | |
Power output | 135 kW (184 PS) @ 5,800 rpm | |
Torque | 275 Nm @ 3,800 rpm | |
Fuel system | Bosch L-Jetronic fuel injection | |
Emissions standard | Pre-Euro (catalyst-equipped from 1979) | |
Compression ratio | 9.0:1 | |
Cooling system | Water-cooled, belt-driven water pump | |
Turbocharger | None | |
Timing system | Single-row timing belt (replaced every 60,000 km) | |
Oil type | Refer to vehicle handbook / manufacturer specification | |
Dry weight | 195 kg |
The BMW M30 B30 (306KA) was used across BMW's E3 and E24 platforms with longitudinal mounting. This engine received platform-specific adaptations-intake tuning in the E3 3.0 CS and emissions calibration in the E24 6 Series-and from 1979 received updated timing belt tensioner design to improve longevity, creating minor service part differences. All adaptations are documented in OEM technical bulletins.
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Field reports and technical service bulletins highlight component wear patterns under high-load operation. Adherence to manufacturer service intervals and approved fluid specifications is critical for long-term reliability.
Analysis derived from manufacturer technical service bulletins and industry workshop records. Repair procedures should follow manufacturer guidelines.
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The M30 B30 (306KA) is fundamentally robust with strong mechanical integrity and proven longevity. Early models (1971–1978) had a known issue with timing belt tensioner wear, but the 1979 update (SIB 11 01 79) resolved this with a revised design. When maintained properly—using correct oil (SAE 10W-40) and adhering to 60,000 km timing belt intervals—these engines are highly durable and suitable for classic car ownership.
The most documented issues are timing belt failure (pre-1979), camshaft wear, cooling system leaks, and fuel injection problems. These are covered in BMW service documentation. While not all units fail, awareness and proactive maintenance—especially timing system care—can prevent major issues.
This 3.0L petrol engine was used in two generations: the E3 3.0 CS (1971–1975) and the E24 6 Series 630 CS (1976–1982). It replaced the earlier M30 B28 and was eventually superseded by the M30 B32. It is part of BMW's legendary inline-six lineage.
Yes, the M30 B30 (306KA) can be tuned. Modifications like performance camshafts, high-flow exhaust, and upgraded intake manifolds can yield +25–40 kW. The stock internals are robust enough for mild upgrades. Classic builds often include dual Weber setups or upgraded L-Jetronic systems. However, ensure cooling and ignition systems are upgraded to handle increased output.
In real-world driving, expect 12.0–15.0 L/100km (19–15 mpg UK) in mixed conditions. Highway efficiency improves to ~11.0 L/100km (~21 mpg UK), while aggressive driving can exceed 17.0 L/100km (14 mpg UK). Fuel economy is consistent across E3 and E24 applications.
Yes, the M30 B30 (306KA) is an interference engine. If the timing belt fails or jumps, piston-to-valve contact is likely, resulting in severe internal damage. While the belt is designed for 60,000 km life, any signs of wear or age should prompt immediate replacement to prevent catastrophic failure.
BMW specifies SAE 10W-40 mineral oil for all M30 B30 (306KA) engines. This viscosity ensures proper lubrication of the camshaft and valvetrain under varied conditions. Change intervals are typically 6,000–10,000 km or annually. Using non-compliant oil can accelerate wear, especially in high-mileage engines.
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GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
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Type-approval guidance and documentation.
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