Forged Pistons for Subaru, EJ257 WRX STI (stroker), 99.75mm, 9:1 (CP Pistons SC7438)
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|
Make |
Subaru |
|
Model |
EJ257 WRX STI (stroker) |
|
Part Number |
SC7438 |
|
Cylinders |
4 |
|
Bore (in) |
3.927 |
|
Bore (mm) |
99.75 |
|
Size |
+0.25mm |
|
Stroke |
83 |
|
Conrod |
130.5 |
|
Comp Height (in) |
1.123 |
|
Comp Height (mm) |
28.5 |
|
Dom/Dish CC |
-17.1 |
|
Compression Ratio |
9 |
|
Weight (Grams) |
394 |
|
Pin (mm) |
23 |
|
Rings |
RS1658-3927-0 |
|
Ring Thickness |
1.2 x 1.2 x 2.0mm |
|
Pin included (Standard) |
905-2500-18CP1S |
|
Upgraded Pin |
905-2500-20CP3S |
|
Ultra Duty Pin |
905-2500-26CP3S |
|
Locks |
905x055 SUB |
CP pistons are compatible with oversized valves and high lift camshafts. CP Pistons represent the highest quality and is engineered for maximum power. Standard features include: Deep valve reliefs accommodate high lift camshafts; Larger valve reliefs for +1mm valve sizes; Custom skirt cam and barrel design; Accumulator grooves; High strength aluminum forgings; High performance rings; Fully CNC machined and balanced to +/- 1 gram; Wrist pins included at no additional cost; Double pin oilers force fed from oil ring groove; Pin lock grooves for easy lock removal; Pin fitting included.
| Product Name | Forged Pistons for Subaru, EJ257 WRX STI (stroker), 99.75mm, 9:1 (CP Pistons SC7438) |
|---|---|
| Brands | CP Carrillo |
| Engine | EJ257 WRX STI |
| Make | Subaru |
Delivery & Freight
We are an Australian-based company that ships items nationally and internationally, usually within 48 hours of receiving your order. High-value items shipped internationally are sent via DHL Express, while lower-value items are sent via Australia Post Express unless otherwise instructed.
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What information do I need to match these pistons to my engine?
You need the engine code, bore size, stroke, rod length, pin diameter and target compression ratio. These determine the correct piston compression height and crown design.
How should ring gaps be set for these pistons?
Ring gaps must be set by your engine builder based on fuel type, boost level and the intended rpm range. Forced-induction engines usually require larger gaps.
Are forged pistons suitable for street engines?
Yes. Forged pistons handle detonation and high cylinder pressure better than cast units. Your builder should set the piston-to-bore clearance to suit your application.
What is the recommended compression ratio for the SC7438 pistons?
The SC7438 pistons have a compression ratio of 9:1, which is suitable for a balance of performance and reliability in a stroker EJ257 WRX STI engine. Ensure that your engine's tuning and fuel quality are compatible with this compression ratio.
What type of wrist pins are included with the SC7438 pistons?
The SC7438 pistons come standard with wrist pins sized at 23mm. Upgraded and ultra-duty pins are also available for those looking to enhance durability under high-performance conditions.
Do the SC7438 pistons require any specific machining before installation?
Yes, the SC7438 pistons require correct bore clearance to be established by the engine builder. It is essential to measure and hone the cylinder bores to ensure proper fit and performance.
Are the SC7438 pistons compatible with high lift camshafts?
Yes, the SC7438 pistons feature deep valve reliefs that accommodate high lift camshafts, making them suitable for performance builds that utilise oversized valves and aggressive cam profiles.
What is the weight of each SC7438 piston?
Each SC7438 piston weighs 394 grams. This lightweight design contributes to reduced reciprocating mass, which can enhance engine response and performance.
