Description

STM Billet Water Neck Replacement Fitting for Evo 8/9

Firstly, Buy STM Billet Water Neck Replacement Fitting for Evo 8/9 with 35mm, -10AN, -12AN and -16AN options. Replace or upgrade your STM water neck setup. The STM Billet Water Neck Replacement Fitting for Evo 8/9 is a replacement outlet fitting designed specifically for the STM billet water neck used on Mitsubishi Lancer Evolution 8 and Evolution 9 cooling systems. If you have changed your radiator, upper radiator hose, or cooling-system configuration, this interchangeable fitting allows you to adapt your STM billet water neck to the hose or AN plumbing required by your current setup. STM offers these fittings separately in multiple outlet configurations, making them a practical solution for Evo owners who want to modify or refresh their cooling-system plumbing without replacing the complete water neck.

STM Billet Water Neck Replacement Fitting for Evo 8/9

The STM replacement fitting is made to work with the STM CT9-BWN billet water neck. The CT9-BWN uses interchangeable outlet fittings, allowing owners to select a 35mm stock-size outlet or AN configurations depending on the cooling-system design. STM lists replacement fittings individually for the 35mm stock hose, -10AN, -12AN, and -16AN options.

This makes the fitting especially useful when an Evo 8 or Evo 9 build evolves over time. For example, a vehicle may originally use a factory-style upper radiator hose and later receive a custom radiator with AN plumbing. Instead of replacing the entire billet water neck, the appropriate STM replacement fitting can be installed to match the new configuration.

Designed for STM CT9-BWN Billet Water Neck

The replacement fitting is intended for the STM billet water neck for Evo 6/7/8/9, rather than being a universal replacement for every factory Mitsubishi water neck. The STM billet water neck uses a modular outlet design specifically so the fitting can be changed when the cooling-system configuration changes.

For Evo 8 and Evo 9 owners, this provides a clean and straightforward way to maintain the STM cooling setup while changing hose routing, radiator configuration, or AN line sizing.

Firstly, the interchangeable design allows you to change the outlet configuration without replacing the complete water neck. Secondly, multiple outlet sizes make the system suitable for both factory-style and custom cooling layouts. Thirdly, replacing only the fitting can be a convenient solution if an existing fitting is damaged, misplaced, or no longer matches the vehicle’s current radiator setup.

Available Outlet Configurations

Depending on the STM water-neck configuration, replacement fittings are available for:

• 35mm stock-size upper radiator hose
• –10AN
• –12AN
• -16AN

These options allow the STM billet water neck to be configured around different radiator and hose requirements. The correct fitting should be selected according to the water neck and cooling-system plumbing installed on the vehicle.

The 35mm option is intended for a stock-size hose configuration, while the AN options are useful for custom cooling systems using AN hose and fittings. This is particularly valuable on performance-oriented Evo builds where aftermarket radiators, relocated components, large exhaust manifolds, or custom hose routing may make the factory-style cooling layout less suitable.

Ideal for Custom Evo Cooling Systems

The STM billet water neck was developed with interchangeable outlet fittings specifically to provide greater flexibility for custom radiator setups. STM also offers AN upper-hose solutions for Evo 7/8/9 applications, including -10AN, -12AN, and -16AN configurations.

A replacement fitting therefore makes sense for an Evo that has received cooling-system upgrades or is being converted from one hose configuration to another. Rather than purchasing another complete water neck, you can select the fitting that corresponds with the desired hose connection.

This is particularly useful for 4G63-powered Evo 8 and Evo 9 builds used for street performance, drag racing, track driving, or custom engine-bay projects where clean and controlled coolant routing is important.

Key Features

• Replacement fitting for STM billet water neck
• Designed for Mitsubishi Evolution 8/9 applications
• Compatible with the STM CT9-BWN billet water neck
• Interchangeable outlet design
• Available in 35mm stock-hose configuration
• Available in -10AN configuration
• Available in -12AN configuration
• Available in -16AN configuration
• Suitable for factory-style or custom cooling-system layouts
• Useful when changing radiator or upper-hose configuration
• Replacement solution without changing the complete billet water neck
• O-ring sealing design for the STM billet water-neck fitting system

Evo 8/9 Fitment

The STM replacement fitting is intended for use with the STM billet water neck fitted to Mitsubishi Lancer Evolution applications. The STM billet water neck itself is listed for Evolution 6, 7, 8, and 9, while this replacement fitting is the appropriate accessory when an existing STM billet water neck needs a different outlet configuration.

For Evo 8 and Evo 9 owners, it is important to confirm that the vehicle is equipped with the STM billet water neck before ordering. This fitting should not be assumed to replace the outlet on a standard OEM Mitsubishi water neck.

Why Replace the Water Neck Fitting?

A change in radiator or coolant plumbing can make the original fitting configuration unsuitable. An Evo owner might move from a factory radiator to an aftermarket radiator, switch from a stock-style hose to AN plumbing, or redesign the engine-bay cooling layout around a larger turbocharger or exhaust manifold.

In these situations, the ability to change only the outlet fitting provides a simple way to adapt the existing STM billet water neck. It also makes maintenance easier if the original fitting has been damaged or needs replacement.

The STM billet water neck itself features a billet aluminum construction, interchangeable fittings, stainless mounting hardware, and an integrated 1/8-inch NPT provision for a water-temperature sensor.

Important Compatibility Note

This product is a replacement fitting for the STM billet water neck. It is not the complete water neck assembly and should not be confused with the factory Mitsubishi water-neck outlet or STM’s older modified OEM water-neck products. STM separately lists the complete CT9-BWN billet water neck and replacement fittings.

Before ordering, confirm that your vehicle has the STM billet water neck and select the fitting size that matches your upper radiator hose or AN cooling-system plumbing.

Frequently Asked Questions

What does this STM replacement fitting fit?

It is designed as a replacement outlet fitting for the STM billet water neck used on Mitsubishi Evolution applications, including Evo 8 and Evo 9.

Is this the complete STM billet water neck?

No. This listing is for the replacement outlet fitting only. The complete STM CT9-BWN billet water neck is sold separately.

What sizes are available?

STM offers replacement fitting configurations for a 35mm stock-size hose, -10AN, -12AN, and -16AN cooling-system connections.

Can I change from a stock radiator hose to AN plumbing?

Yes, provided you have the STM billet water neck and select the appropriate AN replacement fitting and matching hose system. STM specifically designed the billet water neck with interchangeable outlet fittings for this type of configuration change.

Does it fit the factory Mitsubishi water neck?

No. This replacement fitting is designed for the STM billet water neck and should not be treated as a replacement outlet for the standard OEM Mitsubishi water neck.

Is this useful for a modified Evo 8 or Evo 9?

Yes. It is particularly useful when a modified cooling system uses an aftermarket radiator, custom upper radiator hose, or AN plumbing and the existing STM water-neck outlet needs to be changed.

Do I need to replace the whole water neck if I change hose sizes?

Not necessarily. If you already have the STM CT9-BWN billet water neck, its interchangeable design allows the outlet fitting to be changed separately.

What should I verify before ordering?

Verify that your vehicle uses the STM billet water neck and confirm whether your cooling system requires the 35mm, -10AN, -12AN, or -16AN outlet configuration.

Conclusion

The STM Billet Water Neck Replacement Fitting for Evo 8/9 is a practical replacement and upgrade component for Mitsubishi Evolution owners using the STM CT9-BWN billet water neck, providing the flexibility to change between 35mm stock-style, -10AN, -12AN, and -16AN cooling-system outlets as radiator and hose configurations evolve, making it an excellent choice for Evo 8 and Evo 9 street cars, track builds, custom 4G63 cooling systems, and performance projects where clean and properly matched coolant routing matters, so shop and order your STM billet water neck replacement fitting and other Mitsubishi Evo parts from evomotorparts.com today and keep your Evo cooling system configured exactly the way your build requires.

Buy STM Billet Water Neck Replacement Fitting for Evo 8/9 with 35mm, -10AN, -12AN and -16AN options, Replace or upgrade your STM water neck setup.