RCM 2.1 Forged Stroker Kit EJ20


RCM 2.1 Forged Stroker Kit EJ20


ALL Subaru EJ Applications 1992 Onwards


Power, Torque, Strength and reliability. These are all benefits brought to you with the RCM 2.1 stroker kit.

When thinking of purchasing any engine components (in particular a complete stroker kit) it becomes vital that you make your choices wisely. Building a new engine, or rebuilding your existing engine is something you should only need to do once, therefore its important that you use components which are fit for purpose and will provide you with a solid foundation in which to increase power further down the line. With our stroker kits we offer just that:

• Subaru EJ25 Heat Treated Crankshaft

Manufactured by FHI Japan the Subaru Forged Crankshaft is a strong, reliable and proven component. The crank is induction hardened to be extremely resilient to wear and provides a great foundation for any performance engine.

• RCM / Omega Forged Piston Set

RCM have always chosen Omega as their preferred piston manufacturer, not only because of their extensive experience within motorsport but also for the incredible accuracy and attention to detail that is applied to every aspect of their manufacturing.

So why forged?

A forging is still the best way to manufacture a piston, not just from a production point of view but for the strength of the piston. There are certain areas where a piston machined from solid is marginally better than a forging but the strength benefits of a forging far outweigh any benefits of a fully machined piston. You get excellent grain structure when a piston is forged correctly, the way Omega do it. In a fully machined piston you don’t get any true grain flow structure as you are using the material as it is cut from the bar. When you forge the material you create optimal molecular alignment within the material coupled with their own in-house bespoke heat treatment and this is what gives the piston its strength.

CNC (Computer Numeric Controlled) machines are used to do most of the machining that turns a forging into a piston. When finished, the piston is sent to the quality control department to be measured. The quality control department is kept at a constant 20.5°C, important as pistons can expand by as much as 10 microns in sunlight. This way the pistons can also be measured for tolerance 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 when the engine is at full working temperature. Piston skirt profiles are not round but elliptical in shape and barrelled in length. The machining of the skirt is done on extremely accurate machines, capable of holding their repeatability down to 5 microns!

All RCM / Omega Pistons are individually weighed and batched to within 0.5 grams, which ensures that a set of four will have a tolerance deviation of no more than 2.0 grams. On large orders this means that it is not unusual to have a set of 4 pistons with only 0.1 gram deviation!

Both Gobstopper I and II have always used Omega pistons. With both cars developing over 700bhp (plus the additional option of nitrous oxide) and a rev limit of 10,000 rpm you don’t get a greater test for any piston. Omega pistons have always performed faultlessly even under the most extreme of conditions which is why when choosing our preferred manufacturer we wouldn’t look anywhere else.

• RCM / Arrow H Section Connecting Rod Set

Quality. Innovation. Performance. The hallmarks of Arrow Precision. Only the highest quality raw materials, the latest methods and the knowledge of superbly skilled designers and engineers goes into the making of every Arrow Precision Connecting Rod. The high strength RCM H Section Connecting Rod is carefully and precisely manufactured by these very craftsmen using a low sulphur Vacuum de-gassed nickel chrome alloy steel called EN24 in “V condition”, with a pined surface finish. Each rod is ultrasonically tested, crack detected and balanced to within a gram of each other before finally receiving the RCM seal of quality in the form of our laser engraved logo.

• ACL Race Bearings

Used the world over, ACL's reputation speaks for itself. The unique combination of design, metallurgy and engineering come together to deliver what drivers expect from high performance Trimetal engine bearings. Designed to withstand higher RPM conditions, ACL Race Series Engine Bearings feature:

• High strength overlay plate with reduced thickness for improved fatigue properties
• Hardened steel backs on all rod bearings to improve the support of the bearing lining and assist with bearing retention in the housing.
• Increased crush for improved bearing retention
• Elimination of flash plating on the back of the bearings to improve heat transfer through the bearings and to maximize the grip between the bearings and its housing.
• Increased eccentricity to compensate for bore distortion at high rpm and to assist in the formation of hydrodynamic oil films.
• 3/4 grooved Main Bearings to optimize bearing load carrying surface area and oil flow to the conrod bearings.
• Tight consistent wall tolerances to help you maintain consistent clearances.
• Enlarged ID chamfers on bearing edges where required to accommodate large fillet radius on performance crankshafts.

• Engine Block Gasket Kit & Sealer

Included in our stroker kits are the necessary engine short block seals and relevant sealer to ensure you have everything to hand when installing our storker kit. All our gaskets are Genuine Subaru ensuring quality, exact fitment and of course reliability.

Included in the RCM Forged Stroker kit are the following components:

Included in the RCM Stroker kit are the following components:

Subaru Crankshaft

• 79mm Stroke.
• Induction Hardened.

RCM / Arrow Conrod Set

• Big End Diameter: 55.008.
• G/Pin Diameter: 23.000.
• Between Centres: 130.450.
• Big End Width: 21.400.
• Small End Width: 21.400.
• Bolt Size: 3/8 UNF.
• Quantity in Set: 4.

RCM / Omega Forged Pistons

• Forged from 2618A aerospace alloy.
• CNC machined at a constant 20.5°C.
• Weighed and batched to within 0.5 grams.
• Piston sets are supplied with piston rings, gudgeon pins and circlips.

ACL Race Bearing Set

• Rear Thrust Configuaration.
• X1 Big End Bearing Set.
• X1 Main Bearing Set.
• High Performance Trimetal Construction.

Engine Case Seal Kit & Engine Sealer

• X3 Subaru Small Black O-rings for engine block case halves.
• X1 Subaru Orange Block Engine Case O-ring.
• X1 Subaru Front Crank Oil Seal.
• X1 Subaru Rear Crank Oil Seal.
• X6 Dowety Block Bolt Engine Seals.
• X3 Piston Pin Hole Aluminium Seal Washers.
• X1 250gram Tube "Threebond" Grey Engine Sealer.

Additional information

Weight 25 kg
Dimensions 35 × 35 × 35 cm
Piston Size

STD, 0.25mm Oversize Piston Set, 0.50mm Oversize Piston Set