Subaru Cosworth EJ20 and EJ25 Engine Components

Subaru Cosworth. With a 40 year history of excellence in Formula 1 and other high-level Motorsport racing series, every one of Cosworths products is manufactured to the same exacting standards as is required for F1, and are designed to maximise the performance of the vehicle without compromising reliability, consistency, and crucially the driving experience.


Subaru Cosworth EJ25 Big Valve Cylinder Heads

cosworth ej20 and ej25 cylinder heads cosworth ej20 and eh25 cylinder heads cosworth ej20 and ej25 cylinder heads

Cosworth has been the leader in innovative multi valve cylinder head design for over 40 years, and the Cosworth CNC ported big valve cylinder heads are the latest advancement in this technology. Starting with a new OE casting, each head is carefully evuated 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 to yield maximum usable power and response. Each head comes fully assembled with larger valves, multi angle valve seats, high RPM valve springs and titanium retainers. The key features are:

  • New OE casting
  • Enlarged intake and exhaust ports
  • Larger stainless steel intake valves
  • Larger inconel exhaust valves
  • Hi-rev dual valve springs
  • Titanium retainers
  • Hardened steel spring platforms
  • Reshaped combustion chambers
  • Precision multi angle valve seats
  • Machined port bore finish
  • Knife edge port divider
  • Machined Cosworth logo
  • Fully assembled and ready to install
  • Also available with pre-installed Cosworth high performance camshafts as an option

You can review and purchase the Cosworth Subaru EJ25 cylinder heads here:


Subaru Cosworth High-Performance Short Block Assemblies

cosworth ej20 ej25 engine components

Each Cosworth EJ25 short block assembly starts off with all new selected components. Each block is thoroughly inspected before the cylinders are honed to perfection. The rotating assembly which includes a new billet crankshaft, forged steel connecting rods and forged aluminium pistons is then balanced to within 0.5 gram. The Motorsport grade components are then professionally assembled by Cosworth F1 Technicians to ensure a perfect job. Key features:

  • New Subaru EJ25 cylinder block
  • New Subrau forged crankshaft or Cosworth billet crankshaft
  • Cosworth H beam forged steel connecting rods
  • Cosworth forged aluminium pistons
  • Cosworth tri-metal bearings
  • Piston cooling jets
  • Balanced to within 0.5 gram
  • Blue printed assembly

You can review and purchase Subaru Cosworth EJ25 short engines here:


Subaru Cosworth EJ20 and EJ25 Pistons

cosworth ej25 pistons

With 50 years of world class engine design and manufacturing experience, Cosworths intimate knowledge  of the interaction between the piston and other engine components gives them a distinct advantage in piston design ensuring the very finest pistons available anywhere.

All Subaru Cosworth pistons are manufacturered using the same methods employed in Formula 1, and include features such as ant-scuff coating, ultra stong pins, polished crowns and anti-detonation bands. Also, each piston uses a unique forging to minimise weight and maximise strength. Key features:

  • Unique forgings for each application
  • Xylan anti-scuff coating
  • Polsihed crowns for maximum carbon rejection
  • Manufactured from special CosAl 010 material
  • Ultra stong pins
  • Patented anti-detonation bands

Cosworth Subaru EJ20 and EJ25 pistons are available in the following sizes:


Subaru Cosworth EJ25 Billet Crankshafts

cosworth ej25 billet crankshaft

Cosworth billet crankshafts are the ultimate in strength and performance, featuring full flow oiling for superior lubrication during sustained high RPM use. key features:

  • Superior lubrication
  • Profiled counter weights
  • High strength
  • Light weight
  • Isotropic Super Finish for reduced friction

The Subaru Cosworth EJ25 billet crankshafts are available in the following formats:


Cosworth EJ20 and EJ25 Stroker Kits

cosworth ej20 and ej25 stroker kit

Subaru Cosworth stroker kits are the perfect way to add displacement, torque and power to your engine. key features:

  • Cosworth forged pistons and rings
  • Cosworth fully counter weighted billet long stroke crankshaft
  • Cosworth forged steel connecting rods
  • Cosworth tri-metal bearings

The Subaru Cosworth EJ20 and EJ25 stroker kits are available in the following formats:


Cosworth EJ20 and EJ25 Forged Steel Connecting Rods

cosworth ej20 and ej25 connecting rods

The connecting rod is the vital link between the piston and power, so to ensure consistent reliability the standard connecting rods should be replaced for Motorsport grade heavy duty components. Key features:

  • Cosworth tool steel 260,000psi rod bolts
  • Cosworth forging
  • Manufactured from EN24 steel
  • Solid beam design for optimised strength and lightness
  • Radial truss small end design

TheSubaru Cosworth forged steel connecting rods are available in the following formats:


Cosworth EJ20 and EJ25 Cylinder Head Stud kits

cosworth 4G63 cylinder head studs

Essential for high-performance engine builds, Cosworth heavy duty cylinder head stud kits reduce cylinder head movement in high boost and high compression applications, optimising gasket sealing. Key features:

  • Manufactured from H11 tool steel
  • High clamping force
  • Up to 260,000psi tensile strength
  • Roll die formed threads
  • Special heat treatment

You can review and purchase the Cosworth EJ20 and EJ25 180,000psi high performance cylinder head stud kit here

You can review and purchase the Subaru Cosworth EJ20 and EJ25 260,000psi ultra high performance cylinder head stud kit here


Cosworth EJ20 and EJ25 High-Performance Camshafts

cosworth ej20 and ej25 camshafts

Cosworth has been engineering camshafts for 50 years. That coupled with it’s expertise in multi-valve cylinder head design ensures that it’s profiles deliver the very best spread of power across the widest power band. Key features:

  • Ground from new blanks
  • Engineered and tested profiles
  • Broad power band

Cosworth EJ20 and EJ25 high performance camshafts are available with the following profiles:


Cosworth EJ20 and EJ25 High-Performance Valve Springs

cosworth ej20 and ej25 valve springs

Cosworth high rpm and ultra-high rpm valve springs are the result of countless hours of engineering, testing and validation ensuring the best possible performance for sustained high rpm applications. Key features:

  • High rpm springs are manufactured from Japanese Kobe steel
  • High rpm springs are a single design with chamfered ends for ease of installation
  • Ultra-high rpm springs are manufactured from chrome silicon steel, are a dual design and include titanium retainers

Cosworth EJ20 and EJ25 valve springs are available in the following formats:


Cosworth EJ20 and EJ25 Larger Valves

cosworth ej20 and ej25 valves


Larger diameter valves are essential for improved air flow. Cosworth high performance valves are produced from high quality stainless steel. and the exhaust valves are produced from inconel for improved thermal performance. Each valve features a swirl polished back for better airflow, and dished face for additional weight reduction.

Set of Cosworth EJ25 stainless steel inlet valves +1mm (37mm)

Set of Cosworth EJ25 exhaust inconel valves +1mm (33mm)


Cosworth EJ20 and EJ25 Cylinder Head Gaskets

cosworth ej20 and ej25 gasket

Cosworth high performance cylinder head gaskets are engineered to main the crucial seal under the most extreme conditions. Key features:

  • Individual die cut layers of stainless steel
  • Pre-coated with 0.25 micron layer of rubber nitrile
  • Manufactured tolerance of 0.001″
  • Folded “stopper” design for additional clamping around cylinders
  • Available in various thicknesses

Cosworth EJ20 and EJ25 high performance head gaskets are available in the following formats:


Cosworth EJ20 and EJ25 Oil Control

Oil control is absolutely critical to engine performance and reliability so Cosworth pays particular attention to this aspect and offers the following solutions for the EJ engines:

Miscellaneous Cosworth EJ20 and EJ25 Components

Cosworth EJ20 and EJ25 billet timing belt guide

Cosworth billet cam angle sensor bracket

Cosworth EJ25 air pump delete kit

Cosworth thermal composite inlet manifold gaskets

Cosworth high velume intake manifold

Cosworth TGV delete kit

Cosworth kevlar timing belt


A full range of high performance EJ20 and EJ25 engine components can be seen here