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K1 Subaru. Ej-25. 83Mm Dual Thrust C/Shaft

Stock Code:
039ADD830
Stock Level
In Stock
$2,885.83
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K1 - Dual Thrust Crankshaft

Part - 039ADD830 — Subaru EJ‑25 Dual Thrust Crankshaft

  • Application / Fitment
    Designed for Subaru EJ25 engines — including turbo and naturally aspirated versions (WRX/STI/Forester/Liberty with EJ25 platform). It’s a popular choice for stroker builds (2.6 L) when used with matching rods and pistons.

Key Specifications

  • Part Number: 039ADD830 

  • Engine: Subaru EJ25 2.5 L series

  • Stroke: 83.00 mm (increases displacement over the stock 79 mm crank) 

  • Material: Billet 4340 steel — core hardened and nitride treated for strength and fatigue resistance

  • Main Journal Diameter: 60.00 mm — standard Subaru EJ main size

  • Rod Journal Diameter: 52.00 mm (fits Subaru EJ pin size)

  • Flange Type: 8‑bolt crank flange (common EJ pattern) 

  • Dual Thrust Feature: Designed with dual thrust surfaces/locations to support thrust load on both sides of the crank, which helps better handle axial loads and minimizes end‑play — important in stroker builds and high‑load applications.

  • Rear Main Seal: 1‑piece configuration 

  • Bearings: Main and rod bearings not included

  • Reluctor Wheel: Not included — crank position sensor ring typically reused from OEM or aftermarket kit added as needed 

  • Weight: ~21 lb (≈9.5 kg)

  • Finish & Treatment: Magnetic particle tested, straight hole oiling, tight tolerances (~±0.0001″) for journal sizing 

What “Dual Thrust” Means

A dual thrust crankshaft has thrust surfaces machined on both sides of the crank to properly support the crank’s axial movement (end‑play) under load from both flywheel/flexplate and clutch forces. This helps maintain proper crank positioning in the block under heavy use — especially valuable in high‑RPM or race/street stroker engines.

Typical Use & Build Context

  • Commonly used in 83 mm stroker builds that bump the EJ25’s displacement toward approximately 2.6 L when combined with compatible rods (~130.5 mm) and custom pistons. 

  • Often paired with K1 130.5 mm rods (039DD21131) and custom piston kits sized for the desired compression ratio and bore.

  • Requires proper machine‑shop clearancing and setup — clearancing the block and ensuring correct bearing selection is standard for stroker installs.