It's no secret that the OEM Subaru case halves, or "block," aren't exactly the strongest. IAG has developed a process to greatly improve the strength of the OEM Subaru EJ25 Case Halves to combat the effects of high cylinder pressures brought on by increased power and boost. Our proprietary "Closed Deck" System works by supporting the top of the cylinder in the weakest areas and prevents movement and expansion which can lead to cracks and failures. Despite the additional material supporting the cylinder walls, there is no concerns with overheating or coolant flow because the area around the middle of the cylinder still maintains the same coolant area. The custom IAG closed deck inserts are machined with holes for oil and coolant to pass through the same as stock. The IAG 1150 EJ25 Closed Deck Case features threaded and indexed case bolt covers on top of our strongest closed deck inserts. We also machine the 1150 case for Fire-Lock™ head gaskets, 14mm head studs, and add pinned mains and ARP case hardware for ultimate strength. If you're one of those people who prefer to do your own builds we now offer our legendary closed deck case halves for purchase separately. Simply install your crank, rods, and pistons to your own specifications and be confident that the case halves will take the power and prevent common cylinder wall failures. The IAG Closed Deck conversion is performed 100% in-house by our engineers and experts using state-of-the-art equipment. The IAG Closed Deck starts with a new OEM EJ25 bare case. The case is loaded and fixtured to a 4th axis rotary indexer in our Haas VF4-SS CNC Vertical Machining Center. It is supported by the main journals using a precision ground 2-inch bar and tailstock which ensures the datum is the main journals. This method gives us a true reference point to perform all machining operations. A Rennishaw probe is utilized to check that the case is fixtured true, and once confirmed the machining process begins.

IAG 1150 EJ25 Closed Deck Case Includes: (x1) IAG 1150 Closed Deck Converted Case Halves with threaded and indexed case bolt plugs, (x1) Machined for 14mm Head Studs (Head Studs Sold Separately), (x1) Machined for Fire-Lock™ Head Gaskets (Gaskets Sold Separately), (x1) Machined for Pinned Mains, (x1) ARP Case Hardware Set
,Please Note: Overbore must be performed (99.75mm is the preferred bore) before assembly!
,Head Gasket Required: IAG Fire-Lock .051" Head Gaskets with IAG-Spec Alloy Ring Set. IAG-ENG-1740
,Attention: Special note about using ARP Case Bolts - IAG recommends line honing the case when using ARP Case Bolts to remove any distortion created by the hardware. IAG installs ARP CASE BOLTS with 30W engine oil using OEM SUBARU torque specs and procedures. Other torque specs and lubricants may lead to case distortion damage.