Jeep Grand Cherokee WJ 1999-2004 4.7L V8 PowerTech Hurricane Headers HU345STM

Hurricane HU345STM exhaust headers (extractors) are designed for Jeep Grand Cherokee WJ models from 1999–2004 fitted with the 4.7L PowerTech V8 petrol engine.

These headers replace the restrictive factory exhaust manifolds and feature 38mm primary pipes with 51mm outlets. The improved exhaust path is designed to reduce restriction and improve exhaust scavenging, torque, throttle response and usable engine performance.

Important: Aftermarket replacement catalytic converters are required to complete the installation. Oxygen sensor fittings are not supplied or fitted to the headers and must be added where required.

Please check availability and current lead time before ordering.

Key Features

• Designed for Jeep Grand Cherokee WJ 1999–2004
• Suits the 4.7L PowerTech V8 petrol engine
• 38mm primary pipes
• 51mm outlets
• Designed as a performance replacement for the restrictive factory exhaust manifolds
• Designed to improve exhaust gas flow and scavenging
• Helps improve torque, throttle response and engine performance
• Suitable for left-hand-drive and right-hand-drive vehicles

Construction

• High-quality steel tubing
• Quality welded construction for durability
• Thick machined flanges for reliable sealing and durability
• Smooth collector design for improved exhaust gas flow
• Heat-resistant painted finish rated to 800°C

Additional Options

• HG345: Header gasket set
• OSN18M: Oxygen sensor fittings – 2 required
• Ceramic coating: Optional upgrade for improved heat management and surface durability
• Suitable aftermarket replacement catalytic converters
• Professional fitting service available – contact Best Mufflers to arrange installation

Vehicle Fitment

• Make: Jeep
• Model: Grand Cherokee
• Series: WJ
• Year Range: 1999–2004
• Engine: PowerTech V8
• Engine Capacity: 4.7L
• Fuel: Petrol
• Steering: Left-hand drive & right-hand drive

Fitment Notes

• Designed for applicable Jeep Grand Cherokee WJ 1999–2004 4.7L V8 PowerTech models
• Aftermarket replacement catalytic converters are required to complete the installation
• Oxygen sensor fittings are not supplied or fitted to the headers
• Use OSN18M oxygen sensor fittings where required – 2 required
• Recommended header gasket set: HG345
• Suitable for left-hand-drive and right-hand-drive vehicles
• Protect painted or ceramic-coated surfaces during trial fitting and installation
• Clearance may vary depending on engine mount condition, steering components and aftermarket modifications
• Trial fitting is recommended before completing the exhaust system
• Please check availability and current lead time before ordering.

What’s Included

• HU345STM-L left header assembly
• HU345STM-R right header assembly

Recommended With

• HG345 header gasket set
• OSN18M oxygen sensor fittings – 2 required
• Suitable aftermarket replacement catalytic converters
• Replacement manifold studs and nuts where existing hardware is worn or corroded

Why Good Headers & Exhaust Systems Matter

At 4,000 rpm, the 4.7L PowerTech V8 theoretically draws in approximately 9,400 litres of intake air per minute and can expel around 28,200 litres of hot exhaust gas per minute at approximately 600°C.

A well-designed header and exhaust system helps manage this high gas flow efficiently, reducing restriction and improving exhaust scavenging, torque, throttle response and engine performance.

Installation Tips

• Apply penetrating lubricant such as WD-40 or similar to manifold studs, nuts and exhaust fasteners before removal
• Remove all traces of the old manifold gaskets and inspect the cylinder-head sealing surfaces
• Fit new HG345 header gaskets
• Trial-fit both header assemblies and check all clearances before completing the exhaust system
• Protect painted or ceramic-coated header surfaces during trial fitting
• Fit the required OSN18M oxygen sensor fittings in suitable positions
• Install suitable aftermarket catalytic converters and retain the required emissions-control equipment
• Check oxygen sensor wiring for adequate clearance from the headers and other hot exhaust components
• Check clearance around engine mounts, steering components, transmission and surrounding components
• Check all exhaust connections for leaks after installation
• Inspect and re-tighten the header mounting hardware after the initial heat cycles

Warranty & Compliance

Hurricane headers are covered by the manufacturer's applicable warranty conditions.

Installation must retain the catalytic converters, oxygen sensors and any other emissions-control equipment required for the vehicle. Exhaust and emissions requirements vary between Australian states and territories, and the completed installation must comply with the regulations applicable in your state or territory.

FAQ

Which Jeep Grand Cherokee does HU345STM suit?
HU345STM is designed for applicable Jeep Grand Cherokee WJ models from 1999–2004 fitted with the 4.7L PowerTech V8 petrol engine.

Will HU345STM fit a left-hand-drive Jeep?
Yes. HU345STM is listed for left-hand-drive and right-hand-drive Jeep Grand Cherokee WJ 4.7L applications.

Are oxygen sensor fittings included?
No. Oxygen sensor fittings are not supplied or fitted to the headers. OSN18M oxygen sensor fittings are available separately, with 2 required for this installation.

Are header gaskets included?
The recommended header gasket set is HG345. Please select or order the gasket set separately where required.

Do I need replacement catalytic converters?
Yes. Suitable aftermarket replacement catalytic converters are required to complete the installation.

Can HU345STM headers be ceramic coated?
Yes. Ceramic coating is available as an optional upgrade for improved heat management and surface durability. Please contact us for current pricing and lead time.

Can I pick up from the store?
Yes. Pick up is available but must be pre-arranged before collection.

How much is freight?
Freight varies depending on your delivery location and where stock is available. Please contact us for freight charges before ordering. Where possible, we can arrange dispatch from the nearest available product location to help reduce freight costs and delivery times.

Do you ship to the USA?
Yes. Best Mufflers regularly ships exhaust systems and exhaust parts to customers throughout the United States.

Please note that import duties, tariffs, taxes, and customs clearance fees are not included in the product or shipping price. Once your order is processed and the applicable charges are calculated, we will send you a secure payment link to finalise the import duties and tariff charges before dispatch.

Customer Support

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