GSC 4B11 Evo X Exhaust Valves




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GSC Power-Division exhaust valves for the 4B11 Evo X. Exhaust valves are sold as a set of 8 or individually as needed. Choose the standard modified 23-8N stainless material or 2000°F Super Alloy. Available in the standard 29mm size or +1mm oversized. Valve stem diameter is 5.5mm, overall length is 105.85mm.

Vehicle Fitment:
Mitsubishi 4B11
2008-2015 Evolution X

GSC Exhaust Valves:
Part Number: Head Diameter Size: Material: Quantity:
GSC 2021-8 STD Size (29mm) 23-8N Set of 8
GSC 2021-01 STD Size (29mm) 23-8N Single Valve
GSC 2023-8 +1mm (30mm) 23-8N Set of 8
GSC 2023-01 +1mm (30mm) 23-8N Single Valve
GSC 2025-8 STD Size (29mm) Super Alloy Set of 8
GSC 2025-01 STD Size (29mm) Super Alloy Single Valve
GSC 2027-8 +1mm (30mm) Super Alloy Set of 8
GSC 2027-01 +1mm (30mm) Super Alloy Single Valve

Super Alloy:
GSC Power-Division Super Alloy Exhaust Valves are for those running high horsepower, high EGT set ups that need a valve that will last in 2000°F conditions. The Super Alloy Exhaust valves have chrome polished stems to create a smooth, durable finish for added life and better lubricity, especially when paired with the GSC Manganese bronze valve guides. Strength, heat resistance, and performance are engineered into every valve. Under head dish is maximized for weight savings while swirl polished and back cut heads promote better air flow without sacrificing durability.

More Info:
Using advanced 3D design and simulation software, GSC has created a stronger and higher flowing valve head design. GSC flow tests prototype valve heads in the specific applications to ensure the highest flowing valve head available on the market today. With the materials used, GSC offers less valve distortion at the face than any of the tested designs. Less distortion allows for better sealing under extreme conditions and more consistent performance throughout the life of the valve.
  • Swirl polished heads for smoother air flow over the valve
  • Back cut to reduce valve weight for higher RPM, higher boost pressure, and allow for more aggressive cam profiles without increasing valve spring seat pressures
  • Valve stems are micro polished to allow for less oil retention on the stem, which creates less drag on the stem to guide for a smoother motion
  • Intake valves are a modified 21-4n stainless and exhausts are a modified 23-8n stainless material for high heat capacity while maintaining longevity
  • Valve tips are either hardened or have a stelite wafer tip fused so that the tip is within 5 Rockwell C of the rocker or valve tappet for extended life and less wear
  • Valve tip lengths - GSC takes extra time to adjust tip heights on the applications to require less tipping of the valve, to maintain proper tip height for proper valve train geometry, and to cut down on install times when setting valve lash
  • GSC has also adjusted the keeper groove to properly balance intake and exhaust spring pressures to reduce the use of valve spring shims and maximize performance from GSC spring and retainer kits
  • Valves will work with an OEM keeper/lock or, when available, GSC upgraded keeper/lock. It is not mandatory, but it is suggested, that any valve lock not be reused on performance applications due to material grooving
Photos are for reference.

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Customer Reviews

Based on 3 reviews

Fast shipping,good service


Good quality & price

john tonkin (Brisbane, QLD, AU)
Best value valves!

Im really happy I found these over-size GSC power division valves for my 2012 lancer. They are made for EvoX but will fit the N/A 4b11/12 engines straight up. Being a "turbo" valve also means they are perfect for hot n/a Street engines. They have all the flow increasing mods on them: under-cut stems, +1mm over-size heads, 30degree back-cut, dished valve faces & swirl polishing! Can't wait to see what they added on the Flow Bench when combined with the specially profiled GSC power guides as well. Best value performance gear for the 4b1 Mivec engine family on the market!!

Cancer and Reproductive Harm