Subaru’s EJ-series engine has earned its place as a favorite among enthusiasts—not just for its compact, reliable design, but for the nearly endless aftermarket upgrade potential. If you're thinking about modifying or upgrading your EJ, how you plan to use your Subaru should be the main factor guiding your engine build. IAG is widely recognized for their proven, high-performance engine options, with offerings tailored to support everything from spirited street driving to serious track use. In this article, we’ll take a look at IAG’s short block upgrades and long block packages to figure out which setup is the right fit for your EJ build.

The IAG 550 Short Block is our most popular option, offering the best of both worlds—daily reliability and track-ready strength—making it the go-to choice for EJ drivers who want a solid foundation for bolt-ons without going full race build.

The IAG 550 Short Block is a great choice for daily-driven Subarus that occasionally see some spirited driving or track time. Designed to handle up to 550 BHP (around 400 WHP), it’s the ideal solution for drivers seeking a reliable, strengthened engine upgrade without diving into a full race build. As one of IAG’s most popular and economical options, the 550 comes packed with durability-focused features that make it well-suited for supporting common bolt-on upgrades. Also available as a Long Block, the IAG Hand-Built Long Block Package is a complete valve cover to valve cover crate engine designed as a convenient “drop-in” package for those wanting a full engine solution.

Available as a Short Block or a complete drop-in Long Block, the IAG 750 Closed Deck is engineered for those chasing bigger power. With an output rating of 750 BHP (around 560 WHP), it’s ideal for aggressive builds that demand more from their engine—like those with large turbos and upgraded fueling. IAG's proprietary Closed Deck design helps prevent cylinder wall failure by reinforcing the weakest points, making this block a smart upgrade for dual-purpose street and track machines.

Built for serious power, the IAG 750 Short Block is the ultimate foundation for high-horsepower EJ builds with big turbos, upgraded fuel systems, and dual-purpose street and track goals.

The IAG 950’s proprietary Closed Deck design delivers extreme cylinder wall strength, making it the go-to choice for high-RPM, big-power EJ race builds that demand maximum reliability under pressure.

The IAG 950 is a race-ready engine built to handle serious abuse, high RPMs, and big power. Available as a Short Block or complete drop-in Long Block, the 950 features IAG’s proprietary Closed Deck design along with 14mm head studs and the proven Fire-Lock Head Gasket System—the same setup used in our record-setting race cars. Destroker configurations are also available for builds that demand a broader rev range—ideal for road course and circuit racing where you’re staying in the upper RPMs. Not sure if a destroker is right for your setup? Give us a call—we’re here to help.

The IAG 1150 engines are built for serious race applications, designed to endure extreme boost, high cylinder pressure, and repeated abuse. Each engine features IAG’s proprietary Closed Deck design, 14mm head studs, and the Fire-Lock Head Gasket System, offering unmatched durability for high-performance builds. If you're pushing the limits of the EJ platform, the IAG/Crest CNC Stage X 2.5L Billet Aluminum Short Block takes things to the next level. Its billet case is precision machined by Crest CNC, then hand-assembled at IAG to ensure top-tier quality and strength. Both engines are available as short blocks or complete drop-in long blocks.

IAG’s 1150 Short and Long Blocks are purpose-built for serious EJ performance, with Closed Deck strength or full Billet construction for unmatched durability under extreme power.

The IAG Performance Hand-Built Subaru EJ25 Closed Deck Long Block Engine Packages are a complete, valve cover to valve cover, crate engine. If you're looking for a complete "drop-in" package for your Subaru, our long blocks are fully assembled and ready to go.

Not sure whether a short block or long block is the right move for your project? A short block is ideal if your heads and valvetrain are still in good condition and you want to upgrade the bottom end for strength and reliability. On the other hand, a long block offers a fully-assembled, top-to-bottom engine that replaces everything from the oil pan to the valve covers—perfect for complete overhauls, big power goals, or peace of mind. Our fully assembled long blocks also reduce downtime for required cylinder head machine work. If you old engine is still in good running condition you can even resell it and recoupe some of the cost of the new long block. Your choice really comes down to how much you’re looking to replace and how involved you want the build to be.