The BMW M30B35 (346EC) is a 3,430 cc inline — six petrol engine, part of the legendary M30 engine family introduced in 1968. It features a single overhead camshaft (SOHC) design with a chain — driven valvetrain, Bosch Motronic fuel injection, and a compression ratio of 10.0:1. Producing 218 bhp (163 kW) at 5,800 rpm and 310 Nm of torque at 4,000 rpm, it was engineered for smooth operation, refined power delivery, and durability in BMW’s flagship sedans and coupes.
Fitted to the…
The M30B35 (346EC) complies with European emissions standards applicable to vehicles produced between 1988 and 1995 (EU Directive 91/441/EEC, Euro 1).
The BMW M30B35 (346EC) is a 3,430 cc SOHC inline-six petrol engine produced from 1988 to 1995, exclusively for the E32 7 Series. It features Bosch Motronic fuel injection and a chain-driven camshaft, delivering smooth power with proven mechanical durability. Designed to meet Euro 1 regulations, it represents the final evolution of BMW’s naturally aspirated M30 engines.
| Parameter | Value | Source |
|---|---|---|
Displacement | 3,430 cc | |
Fuel type | Petrol (Unleaded RON 95) | |
Configuration | Inline-6, SOHC, 12-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 86.0 mm × 94.6 mm | |
Power output | 218 bhp (163 kW) @ 5,800 rpm | |
Torque | 310 Nm @ 4,000 rpm | |
Fuel system | Bosch Motronic fuel injection | |
Emissions standard | Euro 1 (EU Directive 91/441/EEC) | |
Compression ratio | 10.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | None | |
Timing system | Single-row timing chain | |
Oil type | SAE 10W-40 mineral or semi-synthetic | |
Dry weight | 198 kg |
The BMW M30B35 (346EC) was used in the E32 7 Series platform with longitudinal mounting and rear-wheel drive. It was paired with a 5-speed manual transmission (Getrag 260) or optional 4-speed automatic (ZF 4HP22). No platform-specific tuning or emissions variants were produced. The M30B35 (346EC) was succeeded by the M60B40 V8 in the E38 generation. All data is documented in OEM service manuals and parts catalogues.
The M30B35 (346EC)'s primary reliability risk is timing chain wear due to age or neglect, which can result in bent valves due to its interference design. While the engine block and crankshaft are highly durable, fuel injection wear, valve seal leakage, and distributor cap corrosion are common in high-mileage or poorly maintained examples. UK DVLA MOT failure data from 2020–2023 indicates that 30% of E32 735i models fail due to emissions or idle instability, often linked to fuel injection issues. Adherence to maintenance schedules and use of quality replacement parts are critical for long-term operation.
Analysis derived from BMW technical bulletins (1988–1995), ETK parts documentation, and UK DVLA MOT failure statistics (2020–2023). Repair procedures should follow manufacturer guidelines.
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Yes, the M30B35 (346EC) is mechanically robust and capable of high mileage when properly maintained. Its SOHC design and durable cast-iron block contribute to longevity. The critical maintenance item is the timing chain, which must be inspected every 60,000 km to prevent catastrophic valve damage. With regular oil changes, fuel injection servicing, and attention to cooling system health, the engine can reliably exceed 200,000 km.
Key issues include timing chain wear (due to its interference design), fuel injection faults causing idle and drivability problems, valve seal leakage leading to oil consumption, and distributor cap corrosion causing misfires. These are age-related rather than design flaws and are largely preventable with proper maintenance and use of quality replacement parts.
The M30B35 (346EC) was used exclusively in the BMW 7 Series (E32) 735i model from 1988 to 1995. It was the high-performance petrol engine for this generation and was not offered in any other BMW or MINI model. The engine was succeeded by the M60B40 V8 in later E38 models.
Yes, but within limits. The M30B35 (346EC) can be modified with a performance camshaft, free-flow exhaust headers, and upgraded ignition system to gain 10–20 bhp. However, the stock head and pistons limit high-RPM potential. Some enthusiasts convert to M60-style dual overhead camshafts, but this is complex. Over-boring to 3.8L (M30B38 spec) is also possible for increased displacement.
In the E32 735i, the M30B35 (346EC) achieves approximately 11.5–13.5 L/100km (~24–21 mpg UK) in mixed driving. Highway economy can reach 10.0 L/100km (~28 mpg UK), while city driving may exceed 16.0 L/100km (~18 mpg UK). Fuel economy is highly dependent on driving style, vehicle condition, and fuel system health.
Yes. The M30B35 (346EC) is an interference engine. If the timing chain fails or jumps timing, the pistons will contact the open valves, resulting in bent valves and potentially severe internal damage. This is why strict adherence to the 60,000 km timing chain inspection interval is critical.
BMW recommends SAE 10W-40 mineral or semi-synthetic oil for the M30B35 (346EC), suitable for the engine's hydraulic lifters and camshaft. Oil changes should occur every 10,000 km or annually. Modern API SL/CF 10W-40 oils are compatible and provide adequate protection for both classic and restored applications.
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