PORSCHE 99710490300 Left Engine Motor Cylinder Head 3.8L

( Manufacturer Part Number: 99710490300 ), ( Part Type: Engine Motor Cylinder Head ), ( Id: 8f0eac5b-ea6c-4054-a080-bca8523a9304 ), ( Interchange: 306-50184 ), ( Partout Id: A-133553273 )

Review PORSCHE 997 3.8l Left Side Engine Motor Cylinder Head Assembly fits RWD 911 2005–2008

The **Porsche 997 (911) RWD 3.8L Left-Hand Drive (LHD) Engine Motor Cylinder Head (Part Number: 10490300)** is a meticulously engineered component designed to deliver the legendary performance and reliability synonymous with Porsche s 911 lineup. This cylinder head, manufactured for the **2005 2008 model years**, is a critical part of the **3.8-liter flat-six engine (Type 997)**, renowned for its smooth power delivery and high-revving character. Crafted from high-grade aluminum alloy, the cylinder head features **four valves per cylinder** (intake and exhaust) arranged in a compact, efficient layout to optimize airflow and combustion efficiency. The **hydraulic valve lifters** ensure precise valve timing, reducing wear and maintaining consistent performance over extended periods, while the **integrated camshafts** with their distinctive **double overhead camshaft (DOHC) design** drive the valves with unmatched precision, contributing to the engine s signature throaty exhaust note and responsive throttle response. The cylinder head also incorporates **individual throttle bodies (ITBs)** for each cylinder, enhancing fuel efficiency and power output while allowing for precise engine tuning. This component is fully compatible with the **997 RWD 911 models**, including the **911 Carrera, Carrera S, and Targa**, and is designed to withstand the high stresses of aggressive driving, track use, or high-performance modifications. Whether restoring a classic 911 to its original glory or upgrading an existing engine, this cylinder head ensures a seamless fit, maintaining the engine s structural integrity and performance potential. Built to Porsche s exacting standards, it exemplifies the brand s commitment to engineering excellence, blending durability with the raw driving dynamics that have made the 911 a timeless icon.

### **Pros and Cons of Buying a 2005-2008 Porsche 997 (991.04) RWD 3.8L Left-Hand Drive (LHD) with a Rebuilt Engine (Cylinder Head Work)**

#### **Pros**

1. **Iconic Design and Prestige**

The 997 generation is one of Porsche s most recognizable and desirable 911 models. Its aggressive, angular styling and timeless silhouette make it a head-turner on the road and a status symbol among enthusiasts. The RWD configuration ensures a more traditional, rear-wheel-drive driving experience, which many purists prefer over the later AWD models.

2. **Strong Performance (Stock and Mod Potential)**

The 3.8L flat-six engine in the 997 RWD produces **360 400 horsepower** (depending on tuning) with stock internals, making it quick for its class. The manual transmission (if available) offers engaging, driver-focused shifts, while the PDK (if present) provides near-instantaneous gear changes. The car s weight distribution (50/50 in RWD) contributes to excellent handling, especially on twisty roads.

3. **Reliability Improvements Over Earlier Models**

The 997 generation benefited from refinements over the 996, including better engine management, improved suspension tuning, and more robust internals. The 3.8L engine, while not as high-revving as later models, is generally more forgiving than the 3.6L in the 996. A **rebuilt cylinder head** suggests the seller has addressed a common weak point, extending the engine s lifespan.

4. **Aftermarket and Tuning Support**

The 997 platform has a **thriving aftermarket**, with widespread availability of parts, upgrades, and tuning solutions. Common modifications include:

- **Engine upgrades** (e.g., larger turbos, forged internals, high-flow exhaust)

- **Suspension swaps** (e.g., Bilstein B6, Eibach springs, coilovers)

- **Braking upgrades** (e.g., Brembo calipers, larger rotors)

- **Aesthetic mods** (e.g., carbon fiber hood, wheels, body kits)

This means the car can be easily adapted to modern performance standards.

5. **Lower Running Costs (Compared to Later Models)**

While not cheap to maintain, the 997 is generally **less expensive to service** than newer Porsche models. Parts are still widely available, labor costs are lower, and insurance premiums (for a used car) are reasonable compared to a modern 911.

6. **Driving Experience**

The RWD 997 offers a **more engaging, rear-biased driving feel** than AWD models, with better understeer control and a more forgiving nature on wet roads. The manual transmission (if available) provides a more tactile connection to the car, while the PDK offers near-supercar-level shifts.

7. **Resale Value (For Well-Maintained Examples)**

A **clean, low-mileage 997 RWD with a rebuilt engine** retains value well, especially if it has been well-documented in maintenance. While not as valuable as a 991.2 or 992, it remains a strong investment compared to other used sports cars.

---

#### **Cons**

1. **Engine Reliability Concerns (Pre-Engine Swap Models)**

The **3.8L engine in the 997 (especially pre-2006) is known for cylinder head and valve spring issues**, which can lead to **valve float, exhaust leaks, and catastrophic failure** if neglected. A **rebuilt cylinder head** is a **good sign**, but you should:

- **Verify the rebuild was done by a reputable shop** (look for receipts, work logs, or a pre-purchase inspection report).

- **Check for signs of past issues** (e.g., oil leaks, exhaust smoke, misfires).

- **Ensure the engine has been properly broken in** after the rebuild.

2. **Transmission Wear (Manual and PDK)**

- **Manual transmissions** (if present) can wear out around **80,000 100,000 miles**, especially if the car was driven aggressively.

- **PDK models** (introduced in 2006) have had **transmission failures** in some cases, particularly with **fluid leaks and clutch wear**. A **full PDK service** (if applicable) is essential.

- **Clutch replacement** (for manuals) can cost **$3,000 $5,000** if done properly.

3. **Suspension and Steering Wear**

- **Worn bushings** (control arms, sway bar links)

- **Worn shocks/struts** (especially on high-mileage examples)

- **Power steering leaks** (common in older models)

A **full suspension rebuild** can cost **$2,000 $4,000**.

4. **Electrical Gremlins**

- **Faulty sensors** (e.g., MAF, crankshaft position)

- **Wiring harness problems** (especially in older models)

- **Infotainment glitches** (if equipped with a navigation system)

These can be **expensive to diagnose and fix**, so a **pre-purchase inspection (PPI) is highly recommended**.

5. **Maintenance Costs**

- **Timing belt replacement** ( $1,500 $2,500 every **60,000 80,000 miles**)

- **Spark plugs and coils** ( $500 $1,000 every **30,000 50,000 miles**)

- **Brake jobs** ( $1,000 $2,000 every **20,000 30,000 miles**)

- **Coolant system flushes** ( $300 $600 every **50,000 miles**)

- **Oil changes** ( $150 $300 every **5,000 7,500 miles** with synthetic)

6. **Insurance Costs**

A **well-maintained 997 RWD** will be **more expensive to insure** than a comparable used sports car (e.g., BMW M3, Audi S5) due to Porsche s reputation for high repair costs. Expect **$1,500 $3,000/year** for full coverage, depending on your location and driving history.

7. **Depreciation**

While the 997 holds value better than many sports cars, it **does not appreciate like a 991.2 or 992**. If you plan to sell in **5 10 years**, the return on investment may not be as strong as buying a newer model.

8. **Driving Comfort (Compared to Modern Cars)**

- **Wind noise** (especially at highway speeds)

- **Stiff ride** (unless modified with softer springs)

- **Less advanced driver aids** (no adaptive cruise, lane assist, etc.)

- **Slower acceleration** (compared to a 991.2 or 992)

9. **Parts Availability (Future-Proofing)**

While parts are still widely available, **some components (e.g., rare OEM parts, specific suspension items) may become harder to find** as the model ages. This could increase costs if the car needs **uncommon replacements**.

10. **Potential for Hidden Issues**

- **Rust** (especially in older models, check wheel wells, subframe, and exhaust)

- **Water leaks** (sunroof, windshield, door seals)

- **Exhaust leaks** (common in 3.8L engines)

- **Transmission fluid leaks** (especially in PDK models)

A **thorough inspection by a Porsche specialist** is **mandatory** before purchase.

---

### **Conclusion & Recommendation**

#### **Who Should Buy This Car?**

- You **prioritize driving experience and classic Porsche charm** over modern tech.

- You **plan to invest in maintenance and modifications** (tuning, suspension, brakes).

- You **find a well-documented example with a rebuilt cylinder head** (preferably with **service records**).

- You **don t mind higher insurance and maintenance costs** for the joy of ownership.

- You **intend to keep it for 5 years** (to justify the initial investment).

- You **prefer RWD over AWD** for a more engaging, rear-biased driving feel.

- You **need a daily driver** with low running

Details:

Vehicle Stock #: 740778. Condition: 128k. RH means right or passenger side. LH means left or driver side.

Cylinder Head. All catalytic converters were tested and certified to meet the performance requirements at time of sale. Model: PORSCHE 911. Donor Vehicle Part Information:: BLACK, 041 ,2DR,7/06,CARRERA,BLACK RED ,HAS KEY,3.8L,MANUAL TRANS,RWD.

Seat Cushions do NOT come with airbags.

part #: 99710490300 prices

• $1299.01-$1669.99

specifications cylinderheapar:

• for models: Rwd, 911
• for makes: Porsche
• for years: 2005-2008
• mpn: 99710490300
• part type: Engine Motor Cylinder Head
• id: 8f0eac5b-ea6c-4054-a080-bca8523a9304
• interchange: 306-50184
• partout id: A-133553273

general cylinderheapar:

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

payments cylinderheapar:

• credit card: Visa
• other
• wallet: Paypal

shipping cylinderheapar:

• type: Fixed
• transit: 4-7 Days
• cost: $0.00
• class: Standard
• service: Standard

returns cylinderheapar:

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

seller cylinderheapar:

• # reviews: 30351
• city: Venice, Florida
• rating: 99.8%

offer cylinderheapar:

• quantity: 1
• options: Ship-to-home
• best offers: True
• started: June 11, 2026
• availability: In Stock
• sold: 0

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