GSC Power Division 2005-8 Super Alloy Exhaust Valves STD for 4G63T Evo 1-9/DSM

Vehicle Fitment

• 1992-2006 Mitsubishi Lancer Evolution I-IX (4G63T, AWD)
• 1990-1999 Mitsubishi Eclipse GST / GSX (4G63T, FWD/AWD)
• 1990-1998 Eagle Talon TSi (4G63T, FWD/AWD)
• 1990-1994 Plymouth Laser RS Turbo (4G63T, FWD/AWD)
• 1991-1992 Mitsubishi Galant VR-4 (4G63T, AWD)

Fitment Notes

• Fits all Mitsubishi 4G63T turbocharged applications including DSM 1G (1990-1994) and 2G (1995-1999) platforms, and Lancer Evolution I through IX (1992-2006)
• Does not fit the Lancer Evolution X (4B11T engine) - see GSC 4B11T-specific exhaust valves for that application
• Does not fit the naturally aspirated 4G63 (non-turbo) found in certain Eclipse base trim levels
• Standard (STD) 30.5mm head diameter - confirm existing valve seat diameter before installation; use oversized valves (GSC2007-8) if seats have been previously cut
• Super Alloy material is specifically engineered for high-horsepower, high-EGT builds; for stock or mildly modified applications, the standard 23-8N stainless version (GSC2001-8) is also available

Features

• Exotic Super Alloy construction rated to withstand sustained exhaust gas temperatures up to 2000°F - purpose-built for extreme high-horsepower, high-boost 4G63T applications where standard stainless valves are prone to failure
• Chrome polished valve stems provide a smooth, durable finish that reduces friction and oil retention against the valve guide, delivering added longevity and improved lubricity - especially when paired with GSC Manganese Bronze valve guides
• Swirl polished valve heads promote optimized airflow over the valve face, improving combustion efficiency and supporting peak power output in modified 4G63T applications
• Back-cut head design reduces valve mass, enabling higher RPM capability, increased boost pressure tolerance, and compatibility with aggressive camshaft profiles without elevating valve spring seat pressures
• Maximized under-head dish further reduces valve weight while preserving full structural integrity under sustained high-temperature and high-pressure operating conditions
• Precision-adjusted valve tip lengths minimize tipping requirements at installation, maintaining correct valvetrain geometry and cutting down setup time when setting valve lash
• Engineered keeper groove geometry balances intake and exhaust spring pressures, reducing reliance on valve spring shims and maximizing performance from GSC spring and retainer kits
• Valve tips hardened or stellite-tipped to within 5 Rockwell C of the rocker or tappet contact surface, minimizing tip wear over the service life of the valve
• Less face distortion under extreme operating conditions than competing tested designs, ensuring superior sealing and more consistent performance throughout the life of the valve
• Designed, machined, and validated in-house on CNC machining centers using advanced 3D FEA and real-world flow simulation software with flow testing in the specific application

Specifications

• Position: Exhaust (set of 8 - one per cylinder, full engine set)
• Valve Head Diameter: 30.5mm (STD / Standard Size)
• Valve Stem Diameter: 6.6mm
• Overall Valve Length: 109.20mm
• Material: Super Alloy (exotic high-temperature alloy, 2000°F rated)
• Stem Finish: Chrome polished
• Head Finish: Swirl polished with back cut; maximized under-head dish
• Application Engine: Mitsubishi 4G63T (2.0L DOHC Turbocharged I4)
• Quantity per Set: 8

Included Components

• 8x GSC Power Division Super Alloy Chrome Polished STD Exhaust Valves (30.5mm head, 6.6mm stem, 109.20mm length)

Product Description

The GSC Power Division 2005-8 is a set of eight standard-size (30.5mm) Super Alloy exhaust valves engineered specifically for the Mitsubishi 4G63T turbocharged engine found across the full DSM platform (1990-1999 Eclipse GST/GSX, Eagle Talon TSi, Plymouth Laser RS Turbo, and Galant VR-4) and the complete Lancer Evolution I-IX lineup (1992-2006). Unlike the standard 23-8N stainless GSC exhaust valve (2001-8), the 2005-8 is manufactured from an exotic Super Alloy rated to endure sustained exhaust gas temperatures up to 2000°F - making it the correct choice for high-horsepower, high-boost builds where elevated EGTs push standard stainless valves beyond their thermal limits.

The Super Alloy material provides a decisive advantage in demanding builds running large turbos, aggressive timing, E85, or methanol injection - scenarios where exhaust valve temperatures frequently exceed what conventional stainless alloys can reliably handle over time. The chrome polished stems reduce friction and oil buildup against the valve guide, while the swirl polished and back-cut heads optimize airflow and reduce valve mass for improved high-RPM and high-boost compatibility. GSC further refined keeper groove geometry to balance spring pressures across the valvetrain, and precision-adjusted tip lengths to reduce tipping during installation - both of which translate directly to easier assembly and more consistent valvetrain geometry on rebuilt 4G63T heads.

Sold as a complete engine set of 8, the GSC 2005-8 is a direct-fit replacement for the stock exhaust valves in any standard (uncut) 4G63T cylinder head. For heads that have been machined to oversized seat dimensions, refer to GSC part number 2007-8 (Super Alloy +1mm oversized at 31.5mm). GSC recommends pairing these valves with their Manganese Bronze valve guides (GSC3003-8) and Viton valve stem seals (GSC1002) for a complete, high-performance valvetrain rebuild. This valve is the top-tier exhaust valve in GSC's 4G63T stainless and alloy lineup and is the preferred choice for any serious high-output engine build where longevity under extreme thermal load is a requirement.