The Cosworth Subaru EJ25 CS600 series is designed for extreme track day use and the demanding performance enthusiast. Each assembly is precision built by one of Cosworth’s skilled craftsmen using the finest components from our parts catalog to ensure maximum reliable power and performance. Starting with a new Subaru EJ257 semi closed deck block, we meticulously hone each bore to guarantee perfect piston to cylinder wall clearance. The block is then assembled with our Forged Pistons, motorsport grade Forged H Beam connecting rods along with our high performance rod and main bearings and a new STI Forged crankshaft. For maximum performance, an optional steel billet crank is available (CS600X). Once the cylinder block assembly is completed, we install a pair of our CNC machine port-bored Big Valve Cylinder heads with our proven “S2” camshafts complete with valve lash set to our specifications. The cylinder heads are secured with our high performance 11mm steel studs and sealed with a Cosworth high performance stopper layer steel head gasket. Finally, we install one of our blue-printed, high pressure oil pumps for maximum lubrication. This proven engine combination has been used by top teams to win events in both North Americaand Europe.