Stage X 2.1 Budget Forged Stroker Kit EJ20

Power, torque, strength and reliability. This stroker kit is built from components chosen to give a solid foundation for adding more power later. An engine build or rebuild should only need doing once, so every component needs to be fit for purpose.

Subaru EJ25 heat-treated crankshaft

Made by FHI Japan, the Subaru forged crankshaft is strong, reliable and proven. It is induction hardened for high wear resistance and is a good foundation for any performance engine.

Stage X forged piston set

Forging is still the best way to make a piston, both for production and for strength. A piston machined from solid is marginally better in a few areas, but the strength benefits of a forging far outweigh them. A correctly forged piston has an 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 creates optimal molecular alignment in the material, and combined with 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 measured in a quality control area kept at a constant 20.5°C, because a piston can expand by as much as 10 microns in sunlight. This also means tolerances can be checked anywhere in the world, provided the same 20.5°C conditions are replicated.

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. Skirt machining is done on very accurate machines that hold repeatability down to 5 microns.

Every piston is individually weighed and batched to within 0.5 grams, so a set of four has a deviation of no more than 2.0 grams. On large orders, sets with only 0.1 gram deviation are not unusual.

Manley connecting rod set

Manley H-Beam rods are finished to the same exacting tolerances and quality standards as the Sportsmaster® and Pro Series rods. Final hone size, thread detail, bend and twist are all held to those standards.

ACL Race bearings

Used the world over, ACL combines design, metallurgy and engineering to deliver what drivers expect from high-performance Trimetal engine bearings. Designed for higher rpm conditions, ACL Race Series bearings 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 its housing
• Increased crush for improved bearing retention
• No flash plating on the back of the bearings, to improve heat transfer and maximise the grip between bearing and housing
• Increased eccentricity to compensate for bore distortion at high rpm and to 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