IAG Performance 950 Closed Deck EJ25 Long Block w/ IAG 950 Heads 2002-2014 WRX / 2004-2021 STI / 2004-2013 Forester XT / 2005-2009 Legacy GT

The IAG 950 engine package is designed for customers seeking a complete, race-capable Subaru EJ solution capable of supporting up to 950 BHP with proper supporting modifications. At the core of the package is the IAG 950 Closed Deck Long Block, engineered for extreme cylinder pressure, high boost, and sustained high-horsepower operation.

The foundation begins with a brand new Subaru EJ20 or EJ25 engine case that is converted to a closed deck configuration using IAG’s proprietary insert system. The assembled case halves are CNC machined in-house on a Haas VF-4SS to accept the closed deck inserts, which are thermally installed using a heat-and-freeze process before being machined to a mirror finish. Integrated coolant passages ensure proper cooling and prevent overheating, even in street-driven applications. The block is bored and honed to either 92.5mm or 99.75mm using deck plates on a Sunnen SV-30 honing system, allowing precise piston-to-wall clearances for reduced noise and oil consumption.

Each IAG 950 short block is machined for 14mm head studs and incorporates the Fire-Lock™ head gasket system. This system uses a precision-machined counterbore at the top of each cylinder to accept stainless fire rings that protrude slightly above the deck surface. Combustion sealing is handled by the fire rings, while separate gasket bodies seal oil and coolant passages, resulting in exceptional sealing performance under extreme boost conditions.

The rotating assembly consists of IAG-Spec JE FSR 2618 forged pistons with electroless nickel coating, .250" / .906" H13 tool steel wrist pins, IAG-Spec Tuff H-Beam +2mm connecting rods secured with ARP 625+ rod bolts, and a nitride-treated OEM Subaru STI crankshaft. Each short block is balanced, blueprinted, and assembled by hand using ACL or King Race rod and main bearings. New OEM case bolts and sealant are used during final assembly.

Paired with the short block are the IAG 950 Fully CNC Ported Race Cylinder Heads, designed to deliver maximum airflow for competitive racing environments. These heads begin as brand new Subaru OEM castings sourced directly from Subaru of America. Intake and exhaust ports, including the exhaust dog-leg runners, are CNC machined on a Centroid 5-axis CNC for consistent, repeatable results. Additional machining is performed for large camshaft clearance and 14mm or 1/2" head studs.

The cylinder heads are equipped with +1mm oversized GSC SuperAlloy intake valves, SuperAlloy exhaust valves, GSC manganese-bronze valve guides, GSC Viton valve stem seals, IAG-Spec beehive valve springs with titanium retainers, and OEM keepers. Valve seats are cut using a Newen multi-angle valve job, and the decks are resurfaced on a TS-3000 BlockMate for a smooth, uniform finish. Final assembly includes GSC Power-Division Stage 2 billet camshafts matched with Kelford DLC-coated lifter buckets, with final valve lash set in-house.

IAG 950 Closed Deck EJ25 Short Block:

• Case Halves -Converted to Closed Deck using brand new Subaru OEM case halves, bored and honed to 99.75mm.
• Fire-Lock -IAG Fire-Lock™ receiver groove machining, latest solution to prevent head gasket failure on high horsepower and high boost Subaru's - *IAG Fire-Lock™ head gaskets required
• Head Studs -Machine Case for 14mm head studs - *Head studs are sold separately
• Pistons -IAG-Spec JE FSR 99.75mm 2618 Forged Pistons, Electroless Nickel Plated Tops & Ring area, Ring Set, .250" / .906" H13 Wrist Pins, Clips, (Perfect Skirt Coating and Offset Wrist Pins)
• Connecting Rods -IAG-Spec Tuff H-Beam +2mm / ARP 625+ Rod Bolts.
• Rod / Main Bearings -ACL or King Race bearings.
• Crankshaft -Standard New Subaru Nitride Treated 2017+ STI Crankshaft.
• Case / Main Bolts -Standard FHI Subaru case bolts.

IAG 950 CNC Ported Cylinder Heads:

• Heads - Brand New Subaru OEM WRX STI Cylinder Head Castings
• Machine Porting - CNC Ported Intake and Exhaust Runners
• Intake Valves - GSC 37mm (+1mm) Intake Valves
• Exhaust Valves - GSC 33mm (+1mm) SuperAlloy Exhaust Valves
• Springs / Retainers - IAG-Spec Beehive Valve Springs & Retainers
• Guides - GSC Maganese Valve Guides
• Valve Seals - GSC Valve Stem Seals
• Lifters - Kelford DLC Coated Lifter Buckets
• Camshafts - GSC Stage 2 Billet Camshafts
• Multi-Angle Valve Job
• Machined Cam Lobe Clearance
• Drilled For 14mm Heads Studs
  
• Resurface
• Ultrasonic Cleaning
• Final Lash

Gaskets, Hardware & Accessories:

• Head Studs - IAG / ARP 14mm Set
• Head Gaskets - IAG Fire-Lock™
• Valve Cover Gaskets - OEM
• Cam Seals - OEM
• Valve Covers - OEM
• Wrist Pin Seal, Rear Main Seal & Separator Kit
• Crankshaft Woodruff Key