Engine Mechanical (H4SO) (Except Sti): Overhaul Subaru Impreza GH

DISASSEMBLY

Note. Intake valve rocker assembly cannot be disassembled.

1. Remove the exhaust valve rocker arm from the rocker shaft. NOTE: Keep all the removed parts in order for re-installing in their original positions.
2. Remove the nut and adjusting screw from exhaust valve rocker.

ASSEMBLY

Note. Intake valve rocker assembly cannot be disassembled.

1. Install the adjusting screw and nut to the exhaust valve rocker.
2. Insert the exhaust valve rocker arm to rocker shaft.

Note. Valve rocker arms, and rocker shaft have identification marks. Make sure the parts with same markings are properly assembled.

INTAKE VALVE ROCKER ASSEMBLY

1. If the roller or valve contact surface of valve rocker arm is worn or dented excessively, replace the valve rocker assembly.
2. Check that the valve rocker arm roller rotates smoothly. If not, replace the valve rocker assembly.

Scheme 474

Scheme 475

1. Measure the inner diameter of valve rocker arm and outer diameter of valve rocker shaft, and confirm the difference (oil clearance) between the two values. Clearance between arm and shaft: Standard 0.020 - 0.054 mm (0.0008 - 0.0021 in)
2. If the oil clearance exceeds the limit, replace the valve rocker arm or shaft, whichever shows the greater amount of wear. Rocker arm inside diameter: 22.020 - 22.041 mm (0.8669 - 0.8678 in) Rocker shaft diameter: 21.987 - 22.000 mm (0.8656 - 0.8661 in)
3. If the roller or valve contact surface of valve rocker arm is worn or dented excessively, replace the valve rocker arm.
4. Check that the valve rocker arm roller rotates smoothly. If not, replace the valve rocker arm.

1. Place the cylinder head on the ST. ST 498267800 CYLINDER HEAD TABLE
2. Compress the valve spring and remove the valve spring retainer key using ST. Remove each valve and valve spring.

ST 499718000 VALVE SPRING REMOVER

Scheme 476

Note. Keep all the removed parts in order for re-installing in their original positions. Mark each valve to prevent confusion. Pay careful attention not to damage the lips of intake valve oil seals and exhaust valve oil seals. For removal and installation procedures of the valve guide, intake valve oil seal and exhaust valve oil seal, Refer to "INSPECTION". Refer to VALVE GUIDE , INSPECTION, Cylinder Head. Refer to INTAKE AND EXHAUST VALVE OIL SEAL , INSPECTION, Cylinder Head.

Scheme 477

Scheme 478

1. Install the valve spring and valve. Coat the stem of each valve with engine oil and insert the valve into valve guide. NOTE: When inserting the valve into valve guide, use special care not to damage the oil seal lip. Set the cylinder head on ST. ST 498267800 CYLINDER HEAD TABLE Install the valve spring and retainer. NOTE: Be sure to install the valve spring with its close-coiled end facing the cylinder head side. Set the ST on valve spring. ST 499718000 VALVE SPRING REMOVER Compress the valve spring and fit the valve spring retainer key. After installing, tap the valve spring retainers lightly with a plastic hammer for better seating.