Stage X 2.1 Billet Stroker Kit EJ20

This 2.1 stroker kit for the EJ20 is aimed at power, torque, strength and reliability. A new engine build or rebuild should only need doing once, so each component is fit for purpose and gives a solid foundation for increasing power later on.

79mm billet crankshaft

Reverse engineered from the Subaru crankshaft and made to tight standards from high-quality raw materials, for a strong, light and reliable crank.

Forged piston set

Forging is still the best way to make a piston, both for production and for strength. In some areas a piston machined from solid is marginally better, but the strength benefits of forging far outweigh them. A correctly forged piston has excellent grain structure. A fully machined piston has no true grain flow, because the material is used as it is cut from the bar. Forging gives optimal molecular alignment in the material, and combined with a bespoke heat treatment this is what gives the piston its strength.

CNC (Computer Numeric Controlled) machines do most of the machining that turns a forging into a piston. Finished pistons are then measured in a quality control room held at a constant 20.5°C, because a piston can expand by as much as 10 microns in sunlight. Held at the same 20.5°C, pistons can be measured for tolerance anywhere in the world.

The piston skirt is designed and machined to give a profile that works most efficiently at full working temperature. Skirt profiles are not round but elliptical, and barrelled along their length. The skirt is machined on extremely accurate machines that hold repeatability down to 5 microns.

All pistons are individually weighed and batched to within 0.5 grams, so a set of four has a deviation of no more than 2.0 grams. Sets of four with only 0.1 gram deviation are not unusual.

H-section connecting rod set

The high-strength H-section connecting rods are made from low-sulphur, vacuum de-gassed nickel chrome alloy steel, EN24 in 'V condition', with a peened surface finish. Each rod is ultrasonically tested, crack detected and balanced to within a gram of the others.

ACL race bearings

ACL is used the world over, and its race series Trimetal bearings are designed to withstand higher rpm. They feature:

• High-strength overlay plate with reduced thickness for improved fatigue properties
• Hardened steel backs on all rod bearings, to better support the bearing lining and help retain the bearing in the housing
• Increased crush for improved bearing retention
• No flash plating on the back of the bearings, to improve heat transfer and maximise grip between bearing and housing
• Increased eccentricity to compensate for bore distortion at high rpm and help form hydrodynamic oil films
• 3/4 grooved main bearings to optimise load-carrying surface area and oil flow to the conrod bearings
• Tight, consistent wall tolerances to help maintain consistent clearances
• Enlarged ID chamfers on bearing edges where required, to accommodate the large fillet radius on performance crankshafts

Engine block gasket kit and sealer

The kit includes the short block seals and the relevant sealer needed for installation. All gaskets are genuine Subaru, for quality, exact fitment and reliability.