GSC Power Division 3025-8 Manganese Bronze Exhaust Valve Guide Stopper Subaru EJ

Vehicle Fitment

• 2002-2014 Subaru Impreza WRX (EJ205, AWD, AVCS Intake)
• 2004-2021 Subaru Impreza WRX STI (EJ257, AWD, Dual AVCS)
• 2004-2021 Subaru Impreza WRX STI (EJ257B, AWD, Dual AVCS)
• 2005-2009 Subaru Legacy GT / Outback XT (EJ255, AWD)
• JDM 1999-2007 Subaru Impreza WRX STI (EJ207, AWD)

Fitment Notes

• Stopper-style guide - verify that your cylinder head is machined to accept a guide with a stopper collar before ordering; the traditional smooth-style exhaust equivalent is GSC 3027-8.
• Stopper-style intake equivalent is GSC 3026-8.
• Fits EJ205, EJ207, EJ255, EJ257, and EJ257B engines - does not fit EJ20 SOHC or non-turbocharged EJ25 variants with different valve stem or guide boss specifications.
• Standard OD sizing; light honing of the guide boss may be required depending on head condition and target clearance specification.
• Oversized OD options (+0.001" and +0.003") are available individually for heads requiring bore service.

Features

• Manufactured from true C67410 Manganese Bronze for superior lubricity, heat dissipation, and long-term wear resistance over OEM cast iron guides.
• Stopper collar provides a positive depth-stop during installation, ensuring all eight exhaust guides are driven to a consistent seating depth without repeated measuring.
• CNC-turned on dedicated precision turning centers to maintain the tightest OD-to-ID concentricity tolerances in the aftermarket.
• True-to-size OD minimizes guide boss honing on heads that don't require bore service, reducing overall installation time.
• Profile shaped to improve exhaust port airflow over the OEM guide design.
• Compatible with GSC EJ-series exhaust valves, valve stem seals, and spring kits for a complete matched valvetrain rebuild.

Specifications

• Position: Exhaust
• Style: Stopper Style (with collar)
• Material: Manganese Bronze (proprietary C67410 blend)
• Total Length: 1.873" / 47.57mm
• Outer Diameter: 0.4357" / 11.07mm
• Valve Stem Diameter: 6mm
• Application: Subaru EJ205, EJ207, EJ255, EJ257, EJ257B

Included Components

• 8x GSC Power Division Manganese Bronze Stopper-Style Exhaust Valve Guides (Standard OD)

Product Description

The GSC Power Division 3025-8 is a set of eight stopper-style Manganese Bronze exhaust valve guides engineered for Subaru's turbocharged EJ20 and EJ25 engine family, covering the EJ205, EJ207, EJ255, EJ257, and EJ257B as found in the WRX, WRX STI, Legacy GT, and Outback XT. Manufactured from true C67410 Manganese Bronze, these guides deliver significantly better lubricity, heat conductivity, and exhaust-side wear resistance compared to the factory cast iron replacements - all of which matter in high-boost EJ builds where exhaust gas temperatures and sustained high RPM put constant thermal load on the valvetrain.

The stopper collar integrates a built-in depth reference that seats against the guide boss during installation, eliminating the need to measure seating depth on each of the eight exhaust positions individually. This speeds up the head build process and ensures uniform guide depth across all cylinders. Precision CNC-turned to tight OD-to-ID concentricity tolerances, the 3025-8 requires minimal honing on undamaged guide bosses. For heads requiring bore service, individually sold +0.001" and +0.003" oversized options are available. Builders preferring no stopper should reference the smooth-style GSC 3027-8 instead.

A standard component of serious EJ-platform head builds, the 3025-8 pairs directly with GSC EJ-series exhaust valves, Viton valve stem seals, and beehive or conical spring kits for a complete and properly matched valvetrain on any WRX, STI, Legacy GT, or Outback XT build.