EJ25 Standard Stroke Cosworth Street Tuff Engine
Over the years we have built 100’s of Subaru Engines using various performance parts but nothing to date has matched the quality and reliability of Cosworth high performance components.
As Cosworths Australian Distributer we are able to tailor make Engine packages to suit your HP requirements from our standard stroke EJ20 street tuff applications right through to our EJ25 Stroker race setups.
Due to the shipping weight of Cosworth assembled Engines; we choose to build all Engines in our facility saving you dollars.
A typical Cosworth EJ20/25 Engine has gone through countless hours of dyno evaluation to determine the best combination of parts to guarantee reliable performance.
EJ25 Standard Stroke Cosworth Street Tuff Engine includes:
- New Subaru EJ25 STI Engine case
- New Subaru EJ25 STI Forged Crankshaft
- New STi Forged Connecting Rods
- Cosworth Forged Pistons and rings
- Cosworth Coated, Tri-metal bearings
- Cosworth Head Gaskets
- New Subaru Oil pump
- New Subaru Engine Oil pick up
- New Subaru Engine Oil Sump
- Balanced to within .5 gram
Performance Addon Parts
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The Cosworth Billet timing belt guide replaces the original sheet metal timing belt guide that can flex from belt deflection when subjected to extreme rpms causing the timing belt to skip one or more teeth on the crankshaft sprocket.
Essential for high performance engine builds, heavy duty head studs reduce cylinder head movement in high boost or high compression engines optimising cylinder head to block sealing. Cosworth Ultra High Performance Head Studs are manufactured from H11 tool steel with 240,000+psi tensile strength and come complete with nuts and washers. Manufactured with hex broach end for ease of installation.
The Cosworth Subaru Oil Pan Baffle has been engineered with diverters to control oil returning from the cylinder heads to the pan directing it away from the crankshaft. Additionally, one-way valves prevent oil from reentering the upper crankcase chamber thereby limiting blow by and preventing oil starvation during hard driving.
High performance engines reject a substantial amount of heat through the oil system Maintaining oil pressure and control along with an increase in actual volume will help dissipate heat and stabilize oil temperatures. Cosworth Engine oil pumps are high flowed and pressure blueprinted.
Increased engine performance often means increased engine speed and load. Original factory crankshafts may not be able to withstand the added stress, resulting in catastrophic engine failure. Additionally, many OE crankshafts rod journals are lubricated from only one main oil feed. Cosworth billet crankshafts featurefull-flowoiling whereby each rod journal is lubricated from two main sources. This provides superior lubrication during sustained high rpm use preventing rod bearing failure. Cosworth Subaru crankshafts are manufactured entirely from high grade steel in a light-weight, high strength design with a uniqueIsotropic Super Finish (ISF®).
To ensure engine reliability in all conditions, original connecting rods should be replaced with heavy duty specification parts. Cosworth Forged Connecting Rods are manufactured from high strength 4340 (EN24) steel and machined to exacting tolerances.
Each original cylinder head design is carefully evaluated and tested to establish the improvements required to meet the target performance level. Hours of testing and flow bench validation are used to determine the best advanced port design yielding maximum usable power and response. However, there is more to cylinder head design than just maximum flow. It is critical that port velocity is maintained to ensure drivability and valve train components are matched to guarantee reliable performance. Once all of these factors have been tested and validated, the final port contour is digitized. Using the digitized program, we then reshape both intake and exhaust ports using a 5 axis CNC mill producing an accurate and consistent port shape every time. In addition to re-shaping and enlarging the intake and exhaust ports, most Big Valve Cylinder heads feature a re-shaped combustion chamber to un-shroud the valves increasing air flow and performance. After machining, each cylinder head receives a multi-angle high performance valve job on our precision Newen® CNC valve seat cutter. Then each cylinder head is ultrasonically cleaned, serialized and finally hand assembled with select high performance valve train components, ready to install on your engine.
Cosworth camshaft designs are the most efficient in providing maximum usable power across the widest power band.Each cam is ground from a new blank and finished using the same procedures we use in our extreme level race engines. Cosworth camshafts are profiled to increase boost response thereby increasing engine torque and power.
Cosworth Ultra Race Valve Spring Kits are engineered for use in situations that require valve control in extreme conditions. Each kit consists of dual valve springs with matched lightweight titanium retainers, keepers, and hardened steel spring seats. Cosworth Ultra Race Valve Springs are wound from the highest quality chrome silicone steel with chamfered ends and are heat treated and stress relieved for long term reliability. Ultra Race Valve Spring kits are compatible with Cosworth high performance valves.
Cosworth High RPM Valve Springs are the result of countless hours of engineering, testing and validation ensuring the best possible spring for high performance applications. Cosworth High RPM Valve Springs are wound from the world’s finest Japanese Kobe steel and feature dual chamfered ends to reduce wear on seats and retainers. Each spring has been engineered with increased seat pressure along with higher lift capability for optimum performance potential and improved valve control. Single spring design allows easy installation with no machining required and is perfect for typical high performance use.
Large diameter valves are essential for improved air flow. Cosworth high performance intake valves are produced from high quality stainless steel for maximum durability. Exhaust valves are machined from Inconel for high temperature (2400° F) reliability. Each valve features a swirl polished back for improved air flow and dished face for additional weight reduction. Some Cosworth High Performance Valves are only compatible with Cosworth Ultra Race Valve Spring Kits.
The Cosworth Subaru High Volume Inlet Manifold is cast from aluminum featuring large tapered runners with radiused inlets for improved air flow. Plenum volume has been substantially increased and tuned for power. Engineered for easy installation and is the key to making big power. The Cosworth EJ257 plenum is designed for use with the 2004-2009 STI engines equipped with electronic throttle control. The plenum is not designed for use with any cable-actuated throttle body EJ20/25 applications. This plenum is designed to replace the factory Subaru plenum in vehicles equipped with an aftermarket front-mounted intercooler (FMIC) kit. Throttle body position remains stock, ensuring fitment with any brand FMIC kit designed for the stock throttle body and intake manifold.
The Cosworth Thermal Guard Composite Intake Gasket is designed to aid in the reduction of inlet air temperature by isolating the intake manifold from the heat generated by the engine’s cylinder head. By reducing the temperature of the inlet manifold the temperature of the intake air charge is also reduced. The density of cooler air is greater than that of warm air. A denser intake air charge contains more oxygen which results in the potential for increased power and torque.
The Cosworth Dry Sump Setup Kit for the Subaru EJ series engine is a must for race and performance applications. Dry sump oiling systems offer an unparalleled level of safety and reliability compared to factory Wet Sump systems. Complete crankcase oil scavenging reduces excessive and residual oil that can cause blow-by and power loss. A dry sump also offers more consistent oil pressure to the engine, improved scavenging, and increased ring seal due to greater pan vacuum. The Cosworth Dry Sump System for the Subaru EJ20/EJ25 replaces the original oil sump with a machined from solid, low profile alloy pan with twin scavenge ports, internal baffling and o-ring sealing. A two stage scavenge pump driven by a HTD belt, mounted to a heavy duty bracket evacuates the oil from the engine.
