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ToyotaSubaru WRX/STI Head Stud Installation Guide (EJ20 & EJ25 DOHC Turbo) — CP882
This guide covers installation of the XOTIC PERFORMANCE™ CP882 head stud kit for the 2002–2021 Subaru Impreza WRX and STI — EJ20 2.0L and EJ25 2.5L DOHC turbo engines. The boxer install has one step-order difference from most engines that's worth knowing before you start. Prefer a printable copy? Download the PDF manual.
Why the EJ20 / EJ25 needs head studs
Factory OEM head bolts are torque-to-yield: you torque them to a specified value, then add a final 90° rotation that stretches the bolt to its maximum point. That works at stock power levels. But when you add parts that increase horsepower — a bigger turbocharger, injectors, a tune — you create higher cylinder pressures lower in your RPM range, and the clamping force securing the gasket, head, and block is no longer sufficient. The result: a blown head gasket — a failure mode EJ owners know all too well.
Head studs are engineered to resist stretching. XOTIC PERFORMANCE™ head studs are manufactured from our premium XOTIC 7200 steel alloy, superior in tensile strength to any bolt, and backed by a lifetime warranty. The key to getting that strength into your engine is accurate preload — the tensile force generated when a fastener is tightened, creating clamp force in the joint. Everything in this guide is in service of achieving equal, accurate preload on all 12 studs.
What's in the CP882 kit
- 12 × head studs (XOTIC 7200 alloy)
- 12 × hardened parallel washers
- 12 × nuts
- 1 × socket
- 1 × allen wrench
- 1 × fastener assembly lubricant
Before you start: verify first
Confirm that part number CP882 is compatible with your application (Subaru Impreza WRX / STI turbo — EJ20 2.0L or EJ25 2.5L DOHC turbo) before installing any components. Inspect all package contents and clean as necessary to ensure accurate installation. Report any obvious defects or shipping damage to us before proceeding.
On the EJ, the head goes on first. Unlike most engines where studs thread into the block before the head is set, this procedure installs the head gasket and cylinder head first — then the studs thread in through the head. Follow the step order below as written.
How to install head studs on a Subaru EJ20 / EJ25
- Clean the block threads. Clean the threads in the block prior to installing the head studs to ensure accurate fitment and precise torque readings. A dedicated M11 x 1.25 thread chaser (CS305) makes this fast and protects the threads.
- Set the gasket and head. Install the head gasket and cylinder head, ensuring proper alignment.
- Clean the washer seating areas. Clean the washer seating surfaces on the cylinder head with a fast-evaporating solvent such as non-chlorinated brake cleaner to remove oil, grease, and contaminants. A clean surface is essential for achieving proper fastener preload.
- Install the studs hand-tight. Thread the head studs into the block by hand until snug. Do not apply torque.
- Check stud height with a straightedge. Use a straightedge ruler to measure the distance from the mating surface (deck or main cap) to the top of each installed stud. Ensure all studs of the same length group sit level with each other (within 1 mm / 0.040”). Uneven height may indicate debris or incorrect thread engagement. Properly installed studs will bottom out smoothly and show uniform height across all positions. If a stud appears higher or lower than the others, remove it, re-clean the hole, and reinstall by hand. Do not use tools to force studs deeper. Incorrect stud seating can cause off-angle stress, uneven preload, or stud fracture during engine operation.
- Lubricate. Place the washers onto the studs. Using the supplied assembly lubricant, apply a thin coat to the stud threads, the underside of the nuts, and the top side of the washers.
- Install the nuts. Thread the nuts onto the studs and hand-tighten until they make contact with the washers.
- Torque in sequence. Follow the torque stages below in the numbered sequence shown in the manual's torque sequence diagram.
Subaru EJ20 / EJ25 head stud torque specs
| Stage | Torque |
|---|---|
| 1 | 30 ft-lbs |
| 2 | 60 ft-lbs |
| 3 (final) | 90 ft-lbs |
A common mistake to avoid: when torquing a fastener, do not stop short of the recommended value — continue in one motion until the specified torque is achieved. If you accidentally stop short, loosen the fastener and re-torque. Stopping short and "topping up" produces unequal preload distribution across the studs and risks joint failure.
Frequently asked questions
What are the torque specs for Subaru EJ head studs?
Three stages, following the numbered sequence: 30 ft-lbs, then 60 ft-lbs, then a final pass at 90 ft-lbs.
Which Subarus does the CP882 kit fit?
2002–2021 Impreza WRX and STI models with the EJ20 2.0L or EJ25 2.5L DOHC turbo engine.
Do the studs install before or after the cylinder head?
After — on the EJ, the head gasket and cylinder head are set first, and the studs then thread into the block hand-tight. Follow the guide's step order.
What size thread chaser do I need for an EJ head stud install?
M11 x 1.25 — the CS305 chaser.
Need help?
For technical support, email support@xotic-performance.com. All XOTIC PERFORMANCE™ fasteners are covered by our limited lifetime warranty. Finished your install? Tag #XOTICPERFORMANCE on Instagram for a chance to be featured.
© 2026 XOTIC PERFORMANCE™. This installation guide is an original copyrighted work of XOTIC PERFORMANCE™. Reproduction, distribution, or use of this content in whole or in part without written permission is prohibited. Doc ref: 2025.05.20 (web edition 2026.08).
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