IAG Performance / Crest CNC Stage X 2.5L Subaru Billet Aluminum Short Block For WRX, STI, LGT, FXT

The IAG Performance / Crest CNC 2.5L Subaru Billet Aluminum Short Block aspires to revolutionize the Subaru performance tuning market by reinventing the EJ and addressing virtually every weakness that exists in max-power builds. The Stage X Billet Short Block is engineered to eliminate case flex in high-power EJ builds, making it possible to reliably run at a power output rating of 1150+BHP. This short block is equipped with radiused coolant and oil galleries to improve flow, a 4-bolt bottom end for added strength, and replaceable iron sleeves, making rebuilds easier. If you are looking for an EJ engine that can deliver high horsepower without any compromises, then the Crest CNC/IAG Stage X billet short block is the perfect choice!

The Stage X Billet Short Block is a complete short block built by IAG on the Crest billet platform. Crest CNC (formerly Willall), is renowned for their precision-machined billet aluminum engine blocks and components. With Crest’s proven track record of producing blocks that endure the rigors of high-output engines, combined with our expertise in high-powered aftermarket Subaru builds, this collaboration delivers an unbeatable foundation for those pushing the limits of performance.

The Stage X Billet Short Block case is precision machined by Crest CNC using 6061-T6 Aerospace Aluminum and reinforced with Darton Ductile Iron Sleeves. The billet case halves are meticulously hand-assembled by our expert Subaru technicians, and include the IAG Spec Billet crankshaft, custom IAG-Spec +2mm Tri-Beam connecting rods and ARP 625+ rod bolts, along with IAG Spec JE 99.5mm FSR 2618 forged pistons. The Stage X Short Block also includes ACL or King rod and main bearings and is balanced and blueprinted. Finally, the case halves are sealed with new ARP main/case bolts and sealant.

The IAG Performance / Crest CNC 2.5L Subaru Billet Aluminum Short Block is engineered with numerous advanced features that enhance strength and reliability. Precision machined from solid aluminum billet and hard anodized to prevent marking or staining, this short block is multiple times stiffer and stronger than the stock case, making it ideal for high-powered builds. Additionally, increased material thickness has been strategically added in all known weak points, particularly around the head studs and bottom end location, enhancing the block's resilience.

Additional innovations featured in the Stage X Short Block include a unique 4-bolt bottom end design that provides extra strength and stability. The block’s bolt threads are rolled, rather than conventionally cut, ensuring a solid grip on hardware. Not only does this short block maintain full cooling system operations, but it incorporates the use of its radiused coolant and oil galleries for improved flow and less foaming and/or turbulence. Finally, the Stage X Short Block is compatible with all factory engine bay ancillaries (i.e., AC/PS/etc.).

The IAG Performance / Crest CNC 2.5L Subaru Billet Aluminum Short Block features our proprietary "Fire-Lock" receiver groove machining and is compatible with our IAG "Fire-Lock" Head Gaskets. This system has been proven in our record setting race cars to be the strongest Subaru head gasket system ever produced. To achieve these results, our engineers separated the combustion chamber sealing from the fluid sealing aspects of the head gaskets. Our machinists carefully machine a lip at the top of each cylinder to accept the "Fire-Lock" ring. With the ring locked in place, it stands firmly above the deck, providing a superior seal. The separate gasket bodies take care of sealing oil and coolant passages, while keeping them out of the combustion chamber. 14mm Head studs hold the assembly together. (IAG "Fire-Lock" Head Gaskets and Head Studs Sold Separately).

The IAG Stage X Short Block features JE 99.5mm FSR 2618 custom pistons, engineered to deliver outstanding performance for both street driving, as well as for drag and rally racing applications. These pistons feature thicker ringlands and are treated with electroless nickel-plating, resulting in a stronger piston that can stand up to highly boosted applications. Additionally, they come equipped with .250" / .927” H13 tool steel wrist pins, providing a significant upgrade over standard chromoly pins, ensuring enhanced reliability under extreme conditions.

A common failure point of the OEM Subaru short block are the piston ringlands. The metal ledges on the pistons that hold the compression rings in place can withstand regular usage but are prone to failure when used with modified components. Cracked or broken ringlands often lead to increased oil consumption and eventual bearing failure if the oil is not closely monitored. In contrast, the increased ringland thickness on the custom JE pistons used in the IAG Stage X Short Block are designed to match up to its high-powered capabilities, ensuring durability and reliability even under extreme-performance conditions.

The OEM EJ25 pistons continue to be produced using a hypereutectic cast design, which is susceptible to irregularities in both the casting process and the materials used, leading to potential weaknesses. These cast pistons simply lack the strength needed to handle the extreme power output of this high-performance short block. This is where our custom JE pistons come in; forged from a durable 2618 T6 Alloy with a unique silicone additive, these JE pistons effectively absorb the direct shock and impact of combustion. Engineered to withstand ringland damage due to detonation and preignition, they feature a higher strength material and have been custom designed to feature thicker ringlands.

Our team of certified Subaru specialists at IAG Performance takes great care in assembling each IAG Stage X Short Block. These specialists have now built over 14,000 Subaru engines and counting. Equipped with an advanced selection of tooling and state-of-the-art equipment, we guarantee the quality of all our engine blocks. Each block is meticulously crafted and thoroughly checked, ensuring the highest standards of quality assurance. IAG’s hand-assembled Short Blocks make it easy to upgrade your EJ25 Subaru engine, just leave the technical work to us, and we’ll provide you with a superior short block that’s ready to install.