IAG 550 Long Block Engine w/ IAG 550 Heads for 02-14 WRX, 04-21 STI, 04-13 FXT, 05-09 LGT

Part Details:

The IAG 550 Long Block Engine with IAG 550 Cylinder Heads is a complete, performance-built EJ25 engine package designed for Subaru owners who want a turnkey long block solution without piecing together a short block and heads separately. Built around IAG’s 550-rated bottom end and paired with fully prepared IAG 550 cylinder heads, this long block is engineered to support builds targeting up to 550 BHP with improved durability and consistency over stock.

This setup is a strong choice for performance street builds and moderate turbo upgrades where reliability, smooth power delivery, and long-term engine stability matter.

Vehicle Fitment Overview

Designed for Subaru EJ25-equipped models including WRX, STI, Forester XT, and Legacy GT platforms. Full year-by-year compatibility is listed in the Vehicle Fitment tab above.

This is a performance long block, not a stock replacement. Vehicle configuration, emissions requirements, and overall build goals should always be verified prior to purchase.

What This Long Block Includes

This is a complete long block assembly that includes the short block and fully assembled cylinder heads, along with the gaskets and hardware listed below.

Important Notes: What’s Not Included

• Intake manifold
• Turbocharger and turbo system components
• Fuel system components
• Accessory components (alternator, power steering pump, A/C compressor)
• Timing components unless specifically listed
• ECU calibration (tuning) and supporting modifications

Power & Build Expectations

• Rated for builds targeting up to 550 BHP
• Final power capability depends on turbo system, fueling, cooling, and tuning quality
• Professional installation is strongly recommended
• ECU tuning is required

IAG 550 EJ25 Short Block

• Brand-new Subaru OEM case halves, 99.75mm stock bore
• IAG-spec JE 99.75mm forged pistons with ring set, 0.180″ chromoly steel pins, clips, skirt coating, and offset wrist pin
• IAG-spec H-beam connecting rods with ARP2000 rod bolts
• ACL or King bearings (rod and main)
• New Subaru nitride-treated STI crankshaft (2017+)
• OEM Subaru case and main bolts

IAG 550 Cylinder Heads

• Brand-new Subaru OEM WRX STI cylinder head castings
• GSC 36mm intake valves (standard)
• GSC 32mm exhaust valves (standard)
• GSC valve springs with titanium retainers
• OEM valve guides
• GSC valve stem seals
• OEM lifter buckets
• GSC Stage 1 billet camshafts
• Multi-angle valve job
• Machined cam lobe clearance
• Resurfacing, ultrasonic cleaning, final lash set

Gaskets, Hardware & Accessories

• ARP 2000 11mm head stud set
• OEM head gaskets
• OEM valve cover gaskets
• OEM cam seals
• OEM valve covers
• Wrist pin seal, rear main seal & separator kit
• Crankshaft woodruff key

Installation & Build Notes

• Recommended for performance builds where reliability is a priority
• Supporting modifications (fueling, turbo system, cooling, oiling) should match your power goals
• Break-in procedures and oil selection should follow engine builder recommendations
• Final results depend on the complete setup and professional tuning

Recommended Supporting Upgrades

• Air / Oil Separator (AOS) – helps reduce oil vapor ingestion and protect the intake system
• Oil pickup and baffle upgrades – improves oil control and reduces bearing failure risk
• Long block installation kits – simplifies installation with required gaskets and hardware
• Engine installation fluid kits – includes break-in oil and coolant for first startup

Performance Airflow Upgrades

• Corsa Veloce Stradale Rear-Facing Intake Manifold– increases airflow and supports high-horsepower EJ engine builds

Learn more about IAG Performance engine and reliability solutions