IAG Short Block for Subaru WRX & STI

Closed deck Subaru engine builds engineered for 550, 750, and 900+ horsepower applications.

IAG Closed Deck Short Blocks for Subaru Builds

IAG short blocks are built for Subaru WRX and STI owners looking to support higher horsepower, increased boost, and long-term engine reliability. Whether you’re replacing a failed engine or building a high-performance setup, a closed deck IAG short block provides the foundation for consistent power under load.

Designed for street, track, and high-boost applications, these engine builds eliminate the weaknesses of factory open-deck designs while maintaining proper oiling, cooling, and cylinder stability.

If you’re still mapping out your full build path, our WRX performance upgrade guide breaks down how each stage works together.

If you’re planning a serious build, this is where it starts.

Compare IAG Short Block Options

Choose your short block based on your horsepower goals, driving style, and long-term build plans.

IAG 550 Short Block

Ideal for street builds and moderate power.

Rated for up to approximately 550 BHP
Closed deck reinforcement
Forged pistons and rods
Ideal for daily-driven WRX & STI builds

View IAG 550 Short Blocks

IAG 750 Short Block

For high-boost street and track builds.

Rated up to approximately 750 BHP
Stronger internals and upgraded components
Designed for aggressive tuning setups
Excellent balance of strength and drivability

View IAG 750 Short Blocks

IAG 950 Short Block

Built for extreme horsepower applications.

Rated up to approximately 950+ BHP
Maximum reinforcement and durability
Intended for competition and high-power builds
Supports large turbo and ethanol setups

View IAG 950 Short Blocks

IAG Short Blocks for Subaru WRX & STI

Explore available IAG EJ25 and FA-series short blocks below, organized by engine platform.

IAG EJ25 Short Blocks (WRX STI LGT FXT)

Closed deck EJ25 short blocks engineered for high-boost Subaru WRX and STI builds.

IAG FA-Series Short Blocks (FA20 & FA24 WRX)

Built short blocks for 2015+ WRX FA20 DIT and 2022+ WRX FA24 platforms.

What Makes IAG Short Blocks Different?

IAG short blocks are engineered to correct the structural weaknesses of factory Subaru open-deck engines. Under high boost and elevated cylinder pressure, factory blocks can suffer cylinder wall distortion and head gasket failure. IAG’s closed-deck design reinforces the cylinder walls for improved stability under load.

Each short block is assembled using precision-machined components with carefully matched tolerances. Forged pistons, upgraded rods, reinforced case halves, and performance bearings work together to support reliable power delivery in both street and track builds.

For serious Subaru builds, the short block is not just a replacement component — it is the structural foundation of the entire performance setup.

EJ vs FA Short Block Platforms

Choosing the correct engine platform is critical when upgrading to a built short block.

IAG offers short blocks for:

• EJ25 platforms (2004–2021 STI and select WRX variants)
• FA20 DIT (2015–2021 WRX)
• FA24 (2022+ WRX)

Each engine family uses different internal configurations and supporting components. If you’re unsure which platform your vehicle uses, start with your vehicle hub for the Subaru WRX or Subaru STI to explore compatible engine builds and supporting components.

Frequently Asked Questions About IAG Short Blocks

Is tuning required with an IAG short block?

Yes. A professional ECU calibration is required after installation to ensure proper fueling, ignition timing, and boost control.

What is the difference between 550, 750, and 950 models?

The primary difference is internal strength and horsepower capacity. Higher-tier models use stronger components designed to withstand increased cylinder pressure and extreme power levels.

Can I install an IAG short block with a stock turbo?

Yes, but proper tuning and supporting modifications are still required depending on the vehicle platform.

Does a short block include cylinder heads?

No. A short block includes the engine block, crankshaft, pistons, and connecting rods. Cylinder heads and valvetrain components are separate unless purchasing a long block assembly.

Supporting Mods for Built Short Block Setups

As power increases, the short block becomes only one part of the equation. Supporting components must be upgraded to match the build.

Upgrading to an IAG short block requires supporting modifications to ensure safe operation and long-term reliability under increased power.

Most builds include:

Explore compatible IAG Performance Parts to complete your build as a properly matched system.

Why Buy Your IAG Short Block from Wrench Masters?

At Wrench Masters, we specialize in Subaru performance platforms and high-horsepower engine builds. When you purchase your IAG short block from us, you get:

  • Fast shipping (typically ships in 24–48 hours when in stock)
  • Access to compatible supporting components
  • Assistance selecting the correct engine platform
  • Experience with real-world Subaru builds

We help ensure your engine investment is matched with the right fueling, cooling, and tuning strategy for long-term reliability.

Explore Related IAG Engine Components

A built short block is only one part of a complete Subaru engine setup. For optimal performance and reliability, many builds also include upgraded supporting components from IAG Performance, including:

• High-flow fuel injectors and upgraded fuel delivery components
• Performance intercooler and turbo systems
• Professional ECU calibration and Subaru EFI tuning solutions
• Reinforced performance engine mounts
• Proper crankcase ventilation using an IAG oil catch can system

Explore compatible upgrades to ensure your short block is supported as a complete, properly matched system.

Engine Build Guides

If you’re planning a complete Subaru engine build, these guides can help you choose the right components and understand how different upgrades work together:

• Short Block vs Long Block: Which Is Right for Your Subaru Build?
• How Much Power Can a Stock FA20 or FA24 Handle?