BMW 7646131 Dohc Engine Cylinder Head 3.0L L6 24V N55

( Manufacturer Part Number: 7646131 ), ( Type: Cylinder Head ), ( Manufacturer Warranty: 1 Month ), ( Material: Aluminum ), ( Vintage Part: No ), ( Finish: Unfinished ), ( Country Of Origin: United States )

Review BMW Series 3.0l L6 Dohc 24v N55 Engine Cylinder Head Oem fits 335I E90 2011–2015

The **BMW 7646131 cylinder head** for the **E90 335i (2011 2015)** with the **N55 3.0L inline-six engine** represents a critical high-performance component designed to deliver exceptional power, efficiency, and reliability. This precision-engineered aluminum head features a **DOHC (Dual Overhead Camshaft)** layout with **24 valves**, arranged in a high-flow configuration to optimize airflow for both intake and exhaust strokes. The **four-valve-per-cylinder design** ensures enhanced breathing capacity, allowing the N55 s twin-turbocharged setup to achieve its signature **300 horsepower and 300 lb-ft of torque** with improved throttle response and reduced lag. The head incorporates **pneumatic valve lifters**, which eliminate the need for traditional hydraulic lifters, contributing to smoother operation and reduced friction, while also enabling precise valve timing adjustments for optimal performance.

Constructed from **high-grade aluminum alloy**, the cylinder head is engineered for lightweight durability, balancing strength with weight savings to improve the vehicle s overall power-to-weight ratio. The **intake and exhaust ports** are meticulously machined to maximize airflow efficiency, with the intake ports featuring a **shallow, wide design** to promote smooth air entry, while the exhaust ports are optimized for rapid gas expulsion, aiding in turbocharger spool-up and exhaust scavenging. The head also integrates **BMW s Valvetronic variable valve lift system**, which dynamically adjusts valve lift and duration to fine-tune engine performance across the RPM spectrum, enhancing both power delivery and fuel economy.

For maintenance and longevity, the **N55 cylinder head** includes **separate intake and exhaust camshafts**, each driven by a dedicated timing chain, ensuring precise synchronization with the crankshaft. The **timing chain tensioners and guides** are designed to minimize wear, reducing the risk of chain stretch or failure over time. Additionally, the head features **integrated oil passages and cooling channels**, which help regulate temperature and prevent overheating, particularly under high-load conditions. The **spark plug bores** are precisely drilled to accommodate the **NGK or Bosch spark plugs** used in the N55, ensuring consistent ignition and combustion efficiency.

Whether for a **restoration project, performance upgrade, or replacement due to wear**, this **OEM-spec cylinder head** is a vital component for maintaining the integrity and performance of the **E90 335i s N55 engine**. Its robust construction, advanced valvetronic technology, and high-flow design make it an essential part of BMW s approach to balancing power, responsiveness, and efficiency in its flagship inline-six engines. For enthusiasts seeking to preserve or enhance their vehicle s performance, this head ensures a seamless fit and reliable operation, embodying BMW s commitment to precision engineering.

### **Pros and Cons of Buying a BMW E90 335i (2011 2015) with the N55 Engine**

#### **Pros**

1. **Strong and Reliable Engine**

The N55 is BMW s first turbocharged inline-6 engine, offering a balanced blend of power (300 306 hp) and efficiency. When properly maintained, it can last well beyond 200,000 miles, especially if the turbo, injectors, and oil system are kept in good condition.

2. **Turbocharged Performance**

Unlike naturally aspirated BMW engines of the same era, the N55 delivers strong acceleration (0 60 mph in 5.5 seconds in a well-tuned example) with a linear power delivery. The twin-scroll turbo ensures quick spool-up, making it feel more engaging than older N54 engines in some cases.

3. **Modern Fuel Injection and Turbocharging**

The N55 uses direct injection (unlike the N54 s port-injection), which improves efficiency and reduces carbon buildup on valves. The turbocharging system is more refined than earlier BMW turbo engines, reducing lag compared to the N54.

4. **Good Fuel Economy for a Luxury Sedan**

With proper maintenance, the N55 can achieve **20 25 MPG highway** in a well-tuned E90, which is competitive for a turbocharged luxury sedan of its time. The N55 s efficiency is one of its strongest selling points.

5. **Aftermarket Support and Tuning Potential**

The N55 has a strong aftermarket presence, with tuners like **MHD, JB4, and Apexi** offering reliable upgrades. Stage 1 2 tunes can add **50 100 hp** while improving throttle response. The engine also benefits from **cold air intakes, exhaust upgrades, and turbo backpressure mods**.

6. **Lower Running Costs Than V8 Models**

Compared to BMW s V8 engines (N63, N74), the N55 consumes less fuel, has fewer moving parts, and is generally cheaper to maintain. Parts like the turbo, injectors, and oil pump are more affordable than those in V8 models.

7. **Comfortable and Refined Ride**

The E90 platform is known for its **luxurious interior, quiet cabin, and smooth suspension** (especially with adaptive damping). The 335i strikes a good balance between sportiness and comfort, making it a practical daily driver.

8. **Resale Value and Community**

The N55 has gained a loyal following, and well-maintained examples hold their value better than some older BMW engines. The **E90 335i is a popular choice for enthusiasts**, meaning parts and support are widely available.

9. **AWD Option (xDrive)**

The **335i xDrive** adds all-wheel drive, improving traction in wet or snowy conditions without sacrificing too much performance. This makes it a better all-around choice than the RWD-only version in some climates.

10. **Lower Maintenance Costs Than V8 or Older Engines**

Unlike the **N54 (which suffers from carbon buildup and timing chain issues)**, the N55 is more forgiving if maintained properly. The **oil pump is more reliable**, and the **turbo is less prone to failure** than earlier BMW turbos if kept clean.

---

#### **Cons**

1. **Carbon Buildup on Intake Valves**

While less severe than the N54, the N55 **can still develop carbon deposits** on intake valves due to direct injection. This leads to **rough idle, misfires, and reduced power** over time. **Regular valve cleaning (every 60,000 80,000 miles) is essential** to prevent major issues.

2. **Oil Consumption and Leaks**

Some N55 engines, especially in **higher-mileage examples**, develop **oil leaks** (valve cover gasket, oil filter housing gasket, or oil pan gasket). Additionally, **oil consumption can be an issue** in some units, requiring more frequent top-ups. Always check for **burnt oil smell or blue smoke** from the exhaust.

3. **Turbocharger Reliability Concerns**

While more reliable than the N54, the N55 s **twin-scroll turbo can fail** if not maintained properly. **Clogged oil filters, low oil pressure, or contaminated oil** can lead to turbo damage. **Oil changes every 5,000 7,500 miles (with synthetic oil) are critical.**

4. **Timing Chain Stretch (Less Common Than N54)**

The N55 uses a **timing chain** (not a belt), but it can still stretch over time, leading to **timing issues, misfires, or engine knock**. Some owners report **chain stretch becoming noticeable around 100,000 150,000 miles**, requiring replacement ( $1,500 $2,500).

5. **Electrical and Software Quirks**

Like many BMWs, the E90 can suffer from **electrical gremlins** (faulty sensors, wiring issues, or software glitches). The **N55 s ECU can sometimes misfire or throttle poorly** if sensors (MAF, crankshaft position, etc.) fail. A **full diagnostic check is recommended before purchase.**

6. **Transmission Issues (If Not an Automatic)**

The **6-speed Getrag manual transmission** in the E90 is generally reliable, but some owners report **clutch wear or delayed engagement**. If the car has an **automatic (ZF 6HP21)**, it can be **less smooth** than later BMW automatics and may require **fluid changes every 60,000 miles**.

7. **Rust and Bodywork Concerns**

The E90 is prone to **rust in the wheel arches, rocker panels, and undercarriage**, especially in snowy or salted regions. A **pre-purchase inspection (PPI) is highly recommended** to check for structural corrosion.

8. **Depreciation and Maintenance Costs**

While the N55 is more reliable than the N54, it s still a **BMW**, meaning **parts and labor can be expensive**. A well-maintained N55 will cost more to own than a **Toyota Camry or Honda Accord**, but less than a **V8 BMW or high-mileage N54**.

9. **Limited Aftermarket Parts for Some Components**

While the N55 has good aftermarket support, **some parts (like the turbo, injectors, and oil pump) can be expensive** if they fail. **Buying from a reputable dealer or trusted online seller is crucial.**

10. **Potential for Poor Maintenance History**

Many N55s were **neglected in their early years**, leading to **carbon buildup, oil sludge, and turbo failure**. Always **check service records** and **inspect the engine bay** for signs of neglect (dirty oil, burnt smells, leaks).

---

### **Conclusion**

The **BMW E90 335i (2011 2015) with the N55 engine** is a **strong, efficient, and tunable** choice for those who want a **luxury sedan with sporty performance**. It offers **better reliability than the N54**, **stronger aftermarket support**, and **better fuel economy** than V8 BMWs. However, it **requires diligent maintenance**, particularly in **oil changes, carbon cleaning, and turbo care**, to avoid costly failures.

- Enthusiasts who want a **tunable, turbocharged BMW** with **good daily usability**.

- Buyers who **prioritize efficiency and reliability** over raw power.

- Those who **plan to maintain the car properly** and **budget for potential repairs**.

- **Budget-conscious buyers** who can t afford **regular oil changes and carbon cleaning**.

- Those who **don t want to deal with BMW s electrical quirks**.

- People in **salt-heavy climates** who may face **rust issues** without proper care.

---

### **Recommendation**

**Full service records** (oil changes every 5K 7.5K miles, carbon cleaning done).

**No oil leaks** (check valve cover, oil filter housing, oil pan).

**No carbon buildup** (listen for rough idle, check for misfires).

**Turbo with no signs of failure** (no oil in intake, no excessive lag).

**No rust in critical areas** (wheel arches, subframe, suspension mounts).

**A pre-purchase inspection (PPI) from a trusted mechanic.**

then the **N55 is an excellent buy** one of the best BMW engines of its era.

**If the car lacks documentation, has high mileage without maintenance, or shows signs of neglect (oil sludge, carbon buildup, leaks), it s best to walk away** the long-term costs will outweigh the benefits.

**Buy if

Details:

2011 BMW 3 SERIES RWD SEDAN. May require forklift access.

part #: 7646131 prices

• $495.95-$890.00

specifications cylinderheapar:

• for models: 335i, E90
• for makes: Bmw
• for years: 2011-2015
• mpn: 7646131
• type: Cylinder Head
• manufacturer warranty: 1 Month
• material: Aluminum
• vintage part: No
• finish: Unfinished
• country of origin: United States

general cylinderheapar:

• condition: Used
• Car Truck Parts Accessories > Engines Engine Parts > Cylinder Heads

payments cylinderheapar:

• credit card: Diners-club
• wallet: Apple-pay
• other

seller cylinderheapar:

• rating: 100.0%
• city: Dallas, Texas
• # reviews: 84

offer cylinderheapar:

• quantity: 1
• options: Ship-to-home
• sold: 0
• started: May 20, 2026
• availability: In Stock

shipping cylinderheapar:

• service: Standard
• transit: 6-12 Days
• type: Fixed
• cost: $180.00
• class: Standard

returns cylinderheapar:

• paid by: Buyer
• time: 30 Days
• policy: Returns Accepted

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