IAG Performance Adjustable Timing Idler Kit – Subaru Models (inc. 2002-2014 WRX / 2015-2021 STI)

IAG Adjustable Timing Idler Kit — 2002-2014 WRX / 2015-2021 STI

Dial In Cam Timing After Resurfacing or Thick Gaskets
The IAG Adjustable Timing Belt Idler Kit provides two CNC-machined eccentric idler pulleys that allow precise camshaft timing adjustment on EJ20 and EJ25 engines. This is specifically required after deck resurfacing or when using thicker head gaskets, both of which alter the effective timing belt length and can shift cam timing out of specification. Developed and tested in IAG’s own LIC Time Attack program.

DETAILS

• CNC-machined eccentric idler pulleys — in-house at IAG
• Idler 1: adjusts RIGHT (passenger side) intake and exhaust cams
• Idler 2: adjusts LEFT (driver side) intake and exhaust cams
• Machined 10mm hex on each idler for socket access during timing adjustment
• IAG logo engraved on face
• Manufactured to strict OEM tolerances
• Includes: (2) OEM-quality idlers with CNC-machined eccentrics, (2) M10 zinc-plated bolts
• Highly recommended for any performance EJ20 or EJ25 build with resurfaced heads or thicker head gaskets
• Fits: 2002-2014 WRX / 2015-2021 STI (EJ engines)

Why Resurfacing and Thick Gaskets Affect Cam Timing
When the cylinder head deck or block deck is resurfaced, material is removed, changing the head-to-block relationship. This slightly alters the effective distance the camshaft sprockets sit relative to the crankshaft, which shifts the timing belt’s position and can move cam timing out of specification. Thicker head gaskets (like Fire-Lock rings) create the opposite effect — they increase the head-to-block distance. In either case, the stock timing idlers have no adjustment capability — IAG’s eccentric idlers allow you to correct the cam timing precisely.

CNC Eccentric Design
Each idler uses a CNC-machined eccentric — an offset hole that shifts the idler’s position as it is rotated. The 10mm hex on each idler face allows a socket to hold the idler in position while the retaining bolt is tightened, giving you fine control over the timing adjustment.

Developed in Competition
IAG developed this kit for their own LIC Time Attack program, where resurfaced heads and Fire-Lock head gasket systems are the norm. The kit was proven in competition before it was offered as a product — it is not a theoretical design.

Why Choose IAG Performance

IAG Performance has been building Subaru-specific engine and drivetrain components since 2001, and in that time they have become the standard by which serious Subaru builds are measured. Based in Westminster, Maryland, IAG designs, machines, and assembles their products in-house using Haas CNC equipment and their own engineering team. Their catalog spans everything from short blocks and long blocks rated to 1150 BHP all the way down to the fuel system, oiling, and drivetrain hardware that keeps modified Subarus running reliably for years. Every IAG product exists because a problem needed a better solution than what was available — and the engineering shows.

The RallySport Take

The IAG Adjustable Timing Idler Kit is a mandatory item for any EJ25 build involving deck resurfacing or thicker head gaskets. Without adjustment capability, the cam timing will be off — and cam timing errors on a performance EJ have real power and reliability consequences. If you are building a fire-lock head gasket system or resurfacing the heads, put this kit on the order.

Fitment