The MOST in depth EJ25 rebuild tutorial EVER (wrx/sti)

Introduction

This tutorial provides a comprehensive guide on how to rebuild the EJ25 engine, specifically suited for Subaru WRX and STI models. Based on a detailed video, this step-by-step guide will help you understand the necessary tools, techniques, and best practices for a successful engine rebuild, ensuring performance and reliability.

Step 1: Gather Necessary Tools

• Cam Gear Tool: Essential for timing the engine properly.
• Cam Gear Lock Down Tool: Prevents gear slippage during assembly.
• 14mm 12-point Deep Socket: Specific for Subaru applications.
• ARP Head Studs: Use part number 260-4158 for this rebuild.
• Lubricants: ARP Fastener lubricant and assembly lube.
• Clean Workspace: Ensure a tidy environment to avoid contamination.

Step 2: Prepare the Engine Block

• Unpack and inspect the RA block.
• Clean the deck surface thoroughly to avoid debris.
• Install ARP head studs by:
  • Applying ARP lubricant on threads.
  • Hand-tightening them until snug.

Step 3: Install Cylinder Heads

• Use OEM gasket kit which includes necessary gaskets.
• Ensure the head gaskets are oriented correctly, especially aligning the oil passage holes.
• Visual check of the cylinder head for cleanliness before installation.
• Secure the heads with the ARP studs in a specified torque sequence:
  • First, torque to 30 ft-lbs, then 60 ft-lbs, and finally 90 ft-lbs.

Step 4: Assemble Cylinder Head Components

• Lubricate the camshaft bearings and buckets with assembly lube.
• Install the camshafts, making sure to place them correctly (intake vs. exhaust).
• Attach cam caps and torque them down carefully.

Step 5: Install Oil Pickup and Oil Pan

• Use a new oil pickup from Killer B for reliability.
• Ensure the O-ring is in place to prevent oil leaks.
• Apply silicone sealant to the oil pan surface before installation.

Step 6: Install Water Pump and Timing Components

• Install the water pump with a fresh gasket.
• Attach the timing belt tensioner and ensure proper alignment.
• Use a timing belt with marked alignment for accurate installation.

Step 7: Install Turbo and Exhaust Components

• Attach the turbocharger using a Grim Speed gasket for a secure seal.
• Ensure all exhaust components are tightened properly to prevent leaks.

Step 8: Install Intake Manifold and Associated Components

• Keep the intake manifold assembly complete for easier installation.
• Install intake gaskets and secure the manifold with the provided fasteners.
• Connect all necessary sensors and hoses.

Step 9: Final Assembly and Checks

• Install the alternator, power steering, and any additional components.
• Ensure all wiring and hoses are correctly connected to prevent leaks.
• Check all bolts and fasteners for proper torque.

Step 10: Initial Start-Up and Break-In

• Fill the engine with conventional oil for the first run.
• Start the engine without coolant to check for leaks.
• Monitor oil pressure and listen for any unusual sounds.
• After initial running, drain the oil and replace it with synthetic oil for regular use.

Conclusion

Rebuilding your EJ25 engine requires meticulous attention to detail and the right tools. By following these steps, you can ensure a successful rebuild that enhances your vehicle's performance. Always consult with experts or refer back to this guide as needed during your rebuild process. Happy rebuilding!