IAG PerformanceStage 3 EJ25 Closed Deck Case - 11mm H.S.M. (No Bore / Hone)

Please Note: Overbore must be performed (99.75mm is the preferred bore) before assembly!IAG's Stage 3 Closed Deck converted case halves were created to be the most affordable, cost-effective short block modification for the Subaru EJ25 turbo engines. The deck surface is machined to accept specially CNC'd cast inserts that strengthen the weakest point of the OEM case at the upper sleeve. The factory Subaru EJ25 case is referred to as a semi-open (or semi-closed) deck. The block is essentially an open deck with 3 narrow supports tying in the main case to the tops of the sleeves. This feature was a slight improvement over the EJ20 case, which was a completely open deck with no support. The purpose of the deck supports is to keep the sleeve from moving. While conceptually this is an improvement, the reality is that it simply isn't enough for a high horsepower Subaru. The weakest point of the sleeve is still left open and unaddressed. Our machining process converts the semi-open deck to a complete closed deck and features the use of cast insert material that closely matches the metallurgy of the aluminum case material in a factory Subaru EJ engine block. By using a similar cast material (rather than billet), we ensure that during expansion and contraction the materials grow and shrink at similar rates, which is vital for maintaining roundness within the top of the bore. The outer inserts are machined from 3/4" cast material and the inner inserts from 1-inch cast material. Once the deck is surfaced, the result is a true 1/2 inch finished outer insert thickness and true 3/4 inch finished inner insert thickness. The IAG Closed Deck conversion is performed 100% in-house by our engineers and experts using state-of-the-art equipment.