JAGUAR EAC1639 Engine Cylinder Head 4.2L

( Manufacturer Part Number: EAC1639 ), ( Type: Cylinder Head ), ( Vintage Part: Yes ), ( Country Of Origin: United Kingdom ), ( Performance Part: No )

Review JAGUAR 4.2l Engine Cylinder Head Oem fits XJ6

The **Jaguar EAC1639 XJ6 4.2L Engine Cylinder Head** is a meticulously engineered component that represents the pinnacle of British automotive craftsmanship from the iconic Jaguar XJ6 lineup, particularly the models equipped with the legendary **4.2-liter inline-six (EAC1639) engine**. This cylinder head is a critical element of the powerplant, responsible for housing the combustion chambers, intake and exhaust valves, and the intricate valve train system that governs the engine s performance, efficiency, and longevity. Designed with precision, the head is forged from high-grade **cast iron**, a material chosen for its durability, thermal stability, and resistance to warping under high-temperature conditions qualities essential for maintaining optimal compression ratios and valve sealing in a high-performance engine. The **EAC1639** cylinder head features a **single overhead camshaft (SOHC)** design, driving a pair of **pushrods** that actuate the valves via **rockers**, a configuration that balances simplicity with reliability while delivering a smooth, linear power delivery characteristic of Jaguar s classic V12 and inline-six engines. The head incorporates **four valves per cylinder** (two intake and two exhaust), arranged in a **pent-roof combustion chamber** configuration, which enhances airflow and combustion efficiency, contributing to the engine s robust torque output and refined throttle response. The **intake ports** are generously sized to optimize air intake, while the **exhaust ports** are sculpted to promote efficient scavenging, reducing backpressure and improving exhaust flow critical factors for both performance and drivability. This cylinder head also integrates **hydraulic valve lifters**, eliminating the need for manual adjustment and ensuring consistent valve clearance throughout the engine s operational life, a hallmark of Jaguar s commitment to low-maintenance, high-reliability engineering. For restoration or high-performance applications, the **EAC1639** cylinder head is often paired with upgraded components such as **stainless steel valves, hardened valve seats, or performance camshafts**, allowing enthusiasts to fine-tune breathing and responsiveness while preserving the engine s classic character. Whether restored to its original glory or modified for modern performance, this cylinder head embodies the timeless engineering philosophy of Jaguar where heritage meets precision to deliver an engine that is as elegant in operation as it is powerful in execution.

### **Pros and Cons of Buying a Jaguar EAC1639 XJ6 4.2L Engine Cylinder Head**

1. **Performance Potential** The EAC1639 cylinder head is designed for the Jaguar XJ6 4.2L engine, which is a robust and well-regarded powerplant when properly maintained. With the right modifications, such as porting, polishing, or upgrading valvesprings, it can deliver improved airflow and power, especially when paired with a high-performance camshaft.

2. **Aftermarket Support** This cylinder head has a strong aftermarket presence, meaning parts like valves, springs, retainers, and even full remanufactured heads are widely available. This makes repairs and upgrades more accessible compared to less common engine components.

3. **Compatibility with Modifications** The 4.2L Jaguar engine is a favorite among tuners, and the EAC1639 head is often used in forced induction builds (turbo or supercharged). If you plan to add power, this head can handle it with the right reinforcement (e.g., stronger springs, upgraded valves).

4. **Classic Jaguar Reliability (When Well-Maintained)** Jaguar s 4.2L engines, when properly serviced, are known for durability. The EAC1639 head, in particular, is a later revision that may have minor improvements over earlier versions, reducing the risk of common issues like valve float or excessive wear.

5. **Potential for Restoration Value** If you re restoring a classic Jaguar (such as an XJ6 from the 1980s or early 1990s), a well-maintained or restored EAC1639 head can significantly improve the engine s performance and reliability, enhancing the car s value.

6. **Cost-Effective Replacement Option** Compared to a full engine swap, buying and rebuilding a cylinder head is often more affordable. Remanufactured heads can be a budget-friendly way to revive an engine without the expense of a complete overhaul.

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1. **Common Wear Issues** The EAC1639 head, like many Jaguar cylinder heads, is prone to **valve seat recession** (especially on the exhaust side), **camshaft bearing wear**, and **valve spring fatigue** over time. These issues can lead to leaks, poor compression, or catastrophic failure if not addressed.

2. **Head Gasket Problems** Jaguar 4.2L engines are notorious for **head gasket failures**, often caused by overheating, poor cooling system maintenance, or detonation. Even if the head itself is in good condition, the surrounding engine components may need attention.

3. **Limited Stock Availability** While aftermarket parts exist, **brand-new OEM cylinder heads for the EAC1639 are no longer produced**. This means you ll likely need to source a used or remanufactured head, which may have unknown service history.

4. **Complex Rebuild Process** Rebuilding a Jaguar cylinder head requires **specialized knowledge** of Jaguar-specific tolerances, valve spring pressures, and camshaft profiles. Improper assembly can lead to premature failure, so this job is best left to experienced mechanics.

5. **Potential for Hidden Damage** If purchasing a used head, there s a risk of **internal damage** (e.g., cracked combustion chambers, warped decks, or seized valves) that isn t immediately visible. A thorough inspection (or professional rebuild) is essential.

6. **Compatibility with Modern Fuel Standards** Jaguar s 4.2L engines were not designed for modern fuel standards (e.g., ultra-low sulfur fuels). If the car is being used with modern fuel, **detonation risks increase**, which can damage the head over time.

7. **Weight and Size Considerations** The EAC1639 head is relatively heavy, which can affect engine balance and high-RPM performance. Some tuners opt for lighter aluminum heads from other manufacturers (e.g., Ford or Chevy) for better weight distribution.

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Buying a **Jaguar EAC1639 XJ6 4.2L cylinder head** can be a **cost-effective and performance-enhancing** solution if you re restoring or modifying a classic Jaguar. However, it comes with **significant risks**, particularly regarding **wear, gasket failures, and rebuild complexity**. The head itself is capable of handling **moderate forced induction and high-performance builds**, but only if properly maintained and upgraded.

If your goal is **reliability and longevity**, investing in a **full engine rebuild** (including head work, camshaft, and gasket upgrades) may be more prudent than just replacing the head. If you re **focused on performance gains**, a remanufactured EAC1639 head can be a good choice **provided you address common Jaguar-specific issues** (e.g., valve seats, springs, and cooling system upgrades).

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- **Purchase a remanufactured EAC1639 head** from a reputable supplier (e.g., **Jaguar Performance Parts, Classic Jaguar Engines, or a trusted specialist**).

- **Have it professionally rebuilt** with **new valves, springs, and valve seats** to prevent future failures.

- **Upgrade the cooling system** (thermostat, water pump, radiator) to prevent overheating-related gasket leaks.

- **Consider a camshaft upgrade** (e.g., **Jaguar Performance or Eibach**) for better airflow and power.

- **Pair the EAC1639 head with a forged crank, connecting rods, and pistons** to handle forced induction.

- **Use a high-flow intake manifold** (e.g., **Jaguar Performance or aftermarket**) to maximize airflow.

- **Monitor fuel quality and ignition timing** to prevent detonation, which can destroy the head.

- **Avoid purchasing a used head without inspection** opt for a **fully rebuilt, warrantied unit**.

- **Consider an alternative head** (e.g., **Ford 302 or Chevy LS-based**) if weight and modern manufacturing standards are priorities.

- **Budget for a full engine rebuild** rather than just the head, as surrounding components (camshaft, gaskets, cooling) often need attention.

The **EAC1639 cylinder head is a viable choice for Jaguar enthusiasts** who are prepared for **maintenance challenges** and willing to invest in proper upgrades. However, it is **not a "plug-and-play" solution** success depends on **expertise, quality parts, and diligent upkeep**. If you re not comfortable with Jaguar-specific engine work, consulting a **specialized Jaguar mechanic** before purchasing is highly recommended.

Details:

Please review all the photos for overall condition and ask any questions prior to purchase. Have a Wonderful Day!, ID: 36934. For sale is this Jaguar XJ6 4.2L Engine Cylinder Head OEM EAC1639. Review the pictures, read , and make sure that this is right part for your vehicle.

part #: eac1639 prices

• $674.99-$749.99

specifications cylinderheapar:

• for models: Xj6
• for makes: Jaguar
• mpn: Eac1639
• type: Cylinder Head
• vintage part: Yes
• country of origin: United Kingdom
• performance part: No

shipping cylinderheapar:

• type: Fixed
• transit: 3-9 Days
• class: Economy
• service: Economy
• cost: $0.00

returns cylinderheapar:

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

general cylinderheapar:

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

seller cylinderheapar:

• # reviews: 10052
• city: Snohomish, Washington
• rating: 99.8%

payments cylinderheapar:

• wallet: Paypal
• credit card: Visa
• other

offer cylinderheapar:

• best offers: True
• started: February 2, 2026
• quantity: 1
• options: Ship-to-home
• sold: 0
• availability: In Stock

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