Motor Builds

The best motor build for a WRX, STI, or Evo is a short block matched to the exact engine and the power the car will run: an IAG staged or closed-deck Subaru block for an EJ25, FA20, or FA24 build, a MAPerformance staged shortblock for a 4G63 or Evo X build, or a factory Subaru OEM block for a stock rebuild. IAG and MAPerformance supply most of this collection.

A motor build starts below the cylinder heads. A short block is the assembled block with crank, rods, and pistons, ready for your heads and accessories. A long block adds the heads. Bare case halves are the starting point for a fully custom build. Subaru blocks here also split by deck and rating: closed-deck, BHP-rated blocks for higher-power builds, and standard staged blocks for milder ones. Check your year and model.

IAG Performance, with 23 listings, is the Subaru side, organised as a ladder. It runs from the Stage 1 2.5L short block and 550 Series EJ25 blocks, through closed-deck blocks rated at 600 to 950 BHP in their titles, up to the 1000 FA24 closed-deck short block for the 2022 and later WRX. IAG also lists closed-deck case sets and Crest CNC billet case halves and a Stage X billet short block. Start with IAG when the build is Subaru and target power is already decided.

MAPerformance, with 25 listings, is the Mitsubishi side, plus one Honda application. Its Evo 8 and 9 shortblocks span 2.0L, 2.1L, 2.3L stroker, and 2.4L displacements in Stage 1 and Stage 2 forms, including long-rod versions, while the Evo X range covers 2.0L, 2.2L, and 2.4L blocks such as the SPEC Built 2.0L Stage 2 shortblock for the 2008-2015 Evo X. A Stage 1 Evo 8 4G63 cylinder head and a SPEC L15B7 Stage 1 shortblock for the 2016-2021 Civic 1.5T complete the picture.

Subaru OEM adds nine factory listings, shown without a storefront product link: EJ20, EJ255, and EJ257 short blocks, a Type RA EJ257 block, a 2015-2021 WRX short block, and bare case halves, suiting a like-for-like stock rebuild. P&L Motorsports adds one PS1 EJ25 listing. For the parts that complete a build, see Engine Builds and Connecting Rods, and read Subaru EJ257 Engine: Everything You Need To Know.

What is the difference between a short block and a long block?

A short block is the block assembly without cylinder heads; a long block includes the heads. Most listings here are short blocks or cases, so heads and accessories transfer over or are bought separately.

What does a closed-deck block do?

The IAG closed-deck listings reinforce the top of the cylinder bore area compared with a standard open-deck case. They are the higher-BHP options in this range, named with ratings such as 600, 800, 950, and 1000 BHP.

Does a built short block need a tune?

Plan on professional installation and a tune matched to the finished engine. Do not run a new build on a map written for the old engine.

How do I choose between Stage 1 and Stage 2?

Choose by the power the car will run, not by stage number alone. Match engine, displacement, and fitment years first, then compare the stage or BHP figure in the title.