Jaguar 6 Cylinder Carburettor Conversion

Revitalising Your Classic Jaguar: The 6-Cylinder Carburettor Conversion and Supercharger Rebuild

For enthusiasts of classic Jaguar vehicles, maintaining and enhancing performance is often a labour of love. Whether you own a cherished 6-cylinder model or a more potent XKR or XJR, understanding the available upgrades can significantly impact your driving experience. This article delves into the specifics of a popular 6-cylinder carburettor conversion kit and sheds light on essential rebuild services for the Eaton M112 supercharger found in XKR and XJR models.

The Heart of the Matter: The Jaguar 6-Cylinder Carburettor Conversion Kit

Many classic Jaguar 6-cylinder engines, renowned for their smooth power delivery and distinctive exhaust note, can benefit from a modern carburettor setup. A comprehensive conversion kit aims to replace older, less efficient carburettors with a performance-oriented solution. The core of such a kit typically revolves around high-quality carburettors, meticulously engineered to optimise fuel-air mixture for enhanced power, throttle response, and overall engine efficiency. Let's break down what you can expect to find within a typical kit:

Key Components of the 6-Cylinder Conversion Kit:

• 3 x 45 DCOE 152G Weber Carburettors: These are not just any carburettors; they are the legendary Weber DCOE models, specifically the 45mm 152G variant. The '45' refers to the bore diameter in millimetres, a size often chosen for its balance of performance and tractability in 6-cylinder applications. The 'DCOE' designation signifies a side-draught, twin-choke carburettor, meaning each carburettor handles a specific bank of cylinders or a portion of the engine's intake. The '152G' is a specific model number with particular internal characteristics. The mention of '4 progression hole model' is crucial. Progression holes are small passages within the carburettor that are vital for smooth transition from idle to main jet operation. Having four such holes generally indicates a design aimed at providing a more refined and less abrupt throttle response, particularly at lower engine speeds.
• 1 x Billet Linkage Lever Kit (LP5600): This is the sophisticated system that connects your accelerator pedal to the carburettors, ensuring precise and synchronised operation of the throttle butterflies. A 'billet' component is machined from a solid block of metal, typically aluminium or steel, offering superior strength, durability, and aesthetic appeal compared to cast or stamped parts. The 'linkage lever' specifically refers to the mechanical arms and rods that translate the input from your foot to the opening and closing of the carburettor throttles. A well-designed linkage kit ensures that all carburettors open simultaneously and in a controlled manner, preventing flat spots and ensuring the engine breathes evenly. The LP5600 designation is likely a manufacturer's part number for this specific linkage kit.

Tuning for Success: Jetting Specifications

It's important to understand that simply bolting on new carburettors isn't the end of the story. The optimal performance of your Jaguar's engine will depend heavily on the correct 'jetting'. Jetting refers to the calibration of the various jets (small calibrated orifices) within the carburettor that control the flow of fuel and air. These include main jets, idle jets, air correctors, and emulsion tubes. The kit provider often supplies jetting specifications tailored to engines with varying levels of tune. This means they can offer guidance on which jet sizes to install based on whether your engine is in standard, mildly modified, or more extensively tuned condition. This customisation is key to achieving the best possible performance and drivability.

Supercharger Health: Rebuilds for the XKR and XJR

For owners of the supercharged Jaguar XKR and XJR models, particularly those featuring the Eaton M112 supercharger, maintaining the health of this vital component is paramount. The Eaton M112 is a Roots-type supercharger known for its ability to provide a significant boost in power. Over time, like any mechanical component, it can benefit from a rebuild to ensure optimal performance and longevity. A comprehensive service kit addresses the wear and tear that can occur within the supercharger unit.

What's Inside an Eaton M112 Supercharger Rebuild Kit?

A typical supercharger bearings rebuild and service kit for the Eaton M112 supercharger found in the 4.0 and 4.2 litre XKR and XJR engines will usually contain the following essential items:

• Supercharger Oil (225 ml of synthetic oil) + Filling and Emptying Syringe: The supercharger itself contains a small, dedicated oil reservoir to lubricate the internal gears and rotors. Over time, this oil can degrade or leak. The kit provides the correct grade and quantity of high-quality synthetic oil specifically designed for supercharger use. The inclusion of a syringe makes the often-tricky task of refilling the supercharger with oil a much cleaner and more precise operation. Using the correct oil is critical for the longevity of the supercharger's internal components.
• Uprated Supercharger Coupling: The coupling is a component that connects the supercharger's drive system to the rotors. In some high-performance applications, the standard coupling can be a weak point, especially under increased boost pressures. An 'uprated' coupling is typically made from stronger materials or designed with a more robust construction to withstand higher loads and prevent premature failure.
• Front Snout Bearing x 1: The 'snout' is the front section of the supercharger housing where the drive shaft enters. This section contains a crucial bearing that supports the shaft and allows the rotors to spin freely. This bearing is subject to significant rotational forces and is a common wear item. The kit includes a new, high-quality bearing to replace the old one.
• Rear Snout Bearing x 1: Similar to the front bearing, the rear of the supercharger also typically houses a bearing to support the rotor shaft. This also experiences wear and tear and requires replacement during a rebuild.
• Front Oil Seal: This seal is located around the drive shaft where it exits the snout. Its primary function is to prevent the supercharger oil from escaping and to keep contaminants out. Over time, seals can harden, crack, or lose their sealing ability, leading to oil leaks. A new front oil seal is essential for maintaining the integrity of the supercharger's lubrication system.
• Rear Oil Seal (Implied but often included): While not explicitly listed in the provided text, a comprehensive rebuild kit would typically also include a rear oil seal for the opposite end of the rotor shaft if applicable to the M112's design.

Benefits of Upgrading and Rebuilding

For the 6-cylinder carburettor conversion, the benefits are tangible: improved throttle response, a broader torque curve, potentially more horsepower, and the classic, satisfying sound of triple Webers. For the XKR/XJR supercharger rebuild, the advantages lie in restoring lost performance, preventing catastrophic failure, and ensuring the continued smooth operation of the supercharger, which is integral to the car's character.

Frequently Asked Questions

Q1: Will a carburettor conversion kit fit all Jaguar 6-cylinder models?
While kits are designed for specific engine families, it's always best to confirm compatibility with your exact model year and engine. Variations in intake manifolds and chassis may require minor adaptations.

Q2: Is the Weber carburettor conversion difficult to install?
Installation requires a good understanding of carburettor systems and mechanical aptitude. While the kit provides the core components, you may need additional plumbing, fuel lines, and potentially custom air filters. Professional installation is recommended for those unsure of their mechanical skills.

Q3: How often should the supercharger oil in my XKR/XJR be changed?
While the kit provides oil for a rebuild, regular maintenance schedules for supercharger oil are often not as frequent as engine oil changes. However, it's crucial to check the supercharger manufacturer's recommendations or consult a specialist. A rebuild kit addresses the need for fresh oil during the service.

Q4: Can I just replace the supercharger bearings without replacing the oil?
It is strongly advised against this. Whenever internal components like bearings are replaced, the supercharger oil should also be replaced with the correct, fresh lubricant to ensure proper operation and longevity of the new parts.

Q5: What are the signs that my supercharger needs a rebuild?
Common signs include whining or grinding noises from the supercharger, a noticeable loss of power, or the presence of oil leaks around the supercharger unit. If you suspect an issue, it’s best to have it inspected by a qualified mechanic.

In conclusion, both the carburettor conversion for 6-cylinder Jaguars and the supercharger rebuilds for XKR/XJR models represent significant opportunities to enhance the performance and reliability of these classic vehicles. By understanding the components and benefits involved, owners can make informed decisions to keep their beloved Jaguars running beautifully for years to come.

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