BMW M40 & M60 Engine Restoration & Specs

For many automotive enthusiasts, there's a special kind of satisfaction derived from watching a neglected piece of machinery brought back to its former glory. This is particularly true for engine restorations, where the intricate workings of a powerplant are meticulously brought back to life. Recently, the spotlight has been on the restoration of a BMW M40 engine, specifically from an E30 316i. This series of videos offers a compelling look at the process, showcasing the dedication and skill required to revive these classic powerplants. For those unfamiliar, the M40B16 is a 1.6-litre, naturally-aspirated, four-cylinder engine that found its way into various BMW models during its production run. The E30 316i, the donor vehicle for this particular restoration, is also undergoing its own revival, making the engine's rejuvenation all the more poignant.

The M40 Restoration Journey

While the focus of one particular video segment is on the final stages – the intake manifold and throttle body – the complete restoration is documented across several parts. The initial stages involve a thorough dismantling of the entire intake system, including the throttle body, fuel injectors, and associated components. For anyone with a passion for mechanics and the satisfaction of 'wrenching,' these videos are incredibly therapeutic. They meticulously detail the disassembly of a tired, rusty engine, with each part being carefully cleaned, restored, and then painstakingly reassembled. A notable aspect of this particular M40 restoration is the integration of modern upgrades, such as enhanced fuel injectors, aimed at boosting both power and overall performance. Witnessing the transformation, from the removal of stubborn rust to the application of a fresh, vibrant coat of paint on the manifold, is remarkably cathartic. It's a tangible representation of breathing new life into something old and worn out, restoring it to a condition that should rival its original factory output from the 1980s. There’s a profound sense of accomplishment in this process – taking something that has lost its vigour and revitalising it. Beyond the personal reward, this approach to automotive care is also a form of excellent recycling, conserving resources that would otherwise be spent on developing entirely new vehicles. While many admire such projects, the time, skill, patience, and resources required often place them beyond the reach of the average DIYer, making these detailed video accounts all the more captivating and enjoyable to watch.

The Mighty BMW M60B40: A Deep Dive

Shifting gears from the four-cylinder M40, let's turn our attention to a more potent offering from BMW's past: the M60B40. This V8 engine marked a significant step in BMW's engine development, bridging the gap between the robust straight-sixes like the M50 and the opulent V12s. The M60 series, and specifically the M60B40, replaced the venerable M30B35 and was introduced alongside the smaller M60B30. The M60B40 was a powerhouse, designed for BMW's larger sedans and sporty coupes, gracing models such as the 540i (E34), 740i (E32 and E38), and the sleek 840i (E31). It even found its way into the exclusive De Tomaso Guarà.

M60B40 Technical Specifications

The M60B40 is a 3982cc (243 cu in) V8 engine, featuring an aluminium block with a 90-degree bank angle. Early models, produced until late 1994, utilised Nikasil-coated cylinder sleeves. However, due to concerns about compatibility with lower-quality fuels and the potential for wear, BMW transitioned to Alusil coatings on the cylinder walls, coupled with modified pistons, in later production runs. This makes M60B40 engines manufactured after 1994 generally more desirable, especially in regions with variable fuel quality.

The valvetrain features aluminium cylinder heads with dual overhead camshafts (DOHC), operating four valves per cylinder. Hydraulic lifters are employed for quieter operation and reduced maintenance. The stock camshafts offer a duration of 246/242 degrees with a lift of 9.7/9.4 mm. The throttle body on the M60B40 measures 70 mm in diameter. Ignition is managed by individual coils, and the engine utilises a two-row timing chain with an expected lifespan of 200,000 to 250,000 km (120,000 to 150,000 miles). The engine control is handled by the Bosch Motronic 3.3 system. The M60B40 was a premium engine, and its successor, the M62B44, which offered further refinements, arrived in 1996.

M60B40 Reliability and Common Issues

While the M60B40 is a capable and powerful engine, like any complex piece of machinery, it has its known issues and drawbacks:

1. Rough Idle: Often, a rough idle can be traced back to issues with fuel distribution phase regulation. It's also prudent to check cylinder compression, the Positive Crankcase Ventilation (PCV) system, and the oxygen sensors, as these can all contribute to an uneven idle.
2. High Oil Consumption: Increased oil consumption can be a symptom of worn valve stem seals or piston rings. Replacing the PCV valve is a common first step. If cylinder wear is significant, a more involved solution like re-sleeving the cylinders or replacing the cylinder block may be necessary.
3. Nikasil Coating Wear: As mentioned, the Nikasil coating on the cylinder walls of pre-1994 M60 engines can be susceptible to wear, particularly when exposed to lower-quality fuels. This wear can lead to a loss of cylinder compression. For owners in regions with potentially inconsistent fuel quality, seeking out a post-1994 model with Alusil cylinder walls is advisable.

Servicing the M60B40 can be more expensive than maintaining its M50 counterpart, and fuel economy is also generally higher. These factors, combined with the inherent age of the engines, potentially high mileage, and the possibility of hard use by previous owners, mean that purchasing an M60B40 requires careful consideration. In many cases, opting for the later M62B44 or M62B46 engines might be a more prudent choice for those seeking a robust and modern V8 BMW experience.

Locating the Engine Number

The engine number, a crucial identifier for any vehicle, on the M60B40 is typically found on the right-hand side of the engine block, near the third cylinder, adjacent to the coolant drain plug.

Tuning the M60B40

For those looking to extract more performance from the M60B40, several tuning avenues are available:

• ECU Tuning, Intake, and Exhaust: A good starting point involves upgrading the throttle body (a unit from an M62B44 non-Vanos is often recommended), installing a performance air filter, and fitting a cat-back performance exhaust system. A subsequent ECU tune can then unlock further potential, potentially pushing horsepower figures towards the 300 HP mark.
• Performance Camshafts: Swapping to performance camshafts with increased duration (e.g., 258/258 degrees) and lift (10.5/10.5 mm) can elevate the M60B40's output to over 320 HP. This setup is often considered an optimal balance, providing a significant power increase while remaining suitable for daily driving without major compromise.
• Supercharging: For a more substantial power boost, a supercharger is an attractive option. Kits like the ESS VT1 are designed for a straightforward 'bolt-on' installation onto the stock engine internals. These kits typically operate at around 7 psi (0.5 bar) of boost, which is generally safe for the stock pistons and connecting rods. With this level of boost, the M60B40 can realistically produce around 400 HP, offering a significant increase in performance for high-speed driving.
• Turbocharging: While it's possible to turbocharge the M60B40, it's a considerably more complex and expensive undertaking. The extensive modifications required often make it more practical for enthusiasts to consider purchasing a vehicle that already comes equipped with a more potent factory-tuned engine, such as an E39 M5, rather than embarking on a high-cost turbo conversion.

In conclusion, whether it's the meticulous restoration of an M40 or the performance enhancement of an M60B40, the world of BMW engines offers a rich tapestry for enthusiasts. Understanding the nuances of each powerplant, from their original specifications to their potential for revival and tuning, is key to appreciating these automotive icons.