Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 161

ME(w/o STI)-25

Valve Clearance

MECHANICAL

8. Valve Clearance

A: INSPECTION

1) Disconnect the ground cable from battery.

2) Remove the engine from vehicle. <Ref. to ME(w/

o STI)-29, REMOVAL, Engine Assembly.>

3) Remove the timing belt cover RH. <Ref. to

ME(w/o STI)-47, REMOVAL, Timing Belt Cover.>

4) When inspecting #1 and #3 cylinders

(1) Remove the clip (A) and the stay (B) which

hold the engine harness to the rocker cover RH.

(2) Remove the ignition coil. <Ref. to IG(w/o

STI)-8, REMOVAL, Ignition Coil.>

(3) Disconnect the PCV hose (A) and PCV hose

assembly (B) from the rocker cover RH.

NOTE:

Pinch the clamp of the PCV hose (A) by fitting the

cut out in the ST with the protrusion on the clamp as

shown in the figure, and unlock the clamp.

ST 18353AA000 CLAMP PLIERS

(4) Remove the rocker cover RH.

IN-00203

ME-04652

(A)

(B)

ME-04374

ST

ME-05755

(A)

(B)

ME(w/o STI)-26

Valve Clearance

MECHANICAL

5) When inspecting #2 and #4 cylinders

(1) Remove the secondary air pump. <Ref. to

EC(w/o STI)-29, REMOVAL, Secondary Air

Pump.>

(2) Remove the air duct B (B) from the rocker

cover LH and the air duct A (A).

(3) Remove the ignition coil. <Ref. to IG(w/o

STI)-8, REMOVAL, Ignition Coil.>

(4) Disconnect the PCV hose (A) and PCV hose

assembly (B) from the rocker cover LH.

NOTE:

Pinch the clamp of the PCV hose (A) by fitting the

cut out in the ST with the protrusion on the clamp as

shown in the figure, and unlock the clamp.

ST 18353AA000 CLAMP PLIERS

(5) Remove the rocker cover LH.

6) Turn the crank pulley clockwise until the round

mark and arrow mark on the cam sprocket are set

to position shown in the figure.
NOTE:

Turn the crank pulley using a socket wrench.

• Measurement of clearance of #1 cylinder intake

valve and #3 cylinder exhaust valve

• Measurement of clearance of #2 cylinder ex-

haust valve and #3 cylinder intake valve

• Measurement of clearance of #2 cylinder intake

valve and #4 cylinder exhaust valve

• Measurement of clearance of #1 cylinder ex-

haust valve and #4 cylinder intake valve

ME-04965

(B)

(A)

ME-04374

ST

ME-05757

(A)

(B)

ME-04091

ME-03172

ME-03173

ME-03174

ME(w/o STI)-27

Valve Clearance

MECHANICAL

7) Measure the clearance of intake valve and ex-

haust valve using thickness gauge (A).
NOTE:

• Insert a thickness gauge in a direction as hori-

zontal as possible with respect to the valve lifter.

• Lift up the vehicle, and then measure the ex-

haust valve clearances.

• If the measured value is not within the inspection

value, take notes of the value in order to adjust the

valve clearance later on.
Valve clearance (inspection value):

Intake

0.20

+0.04

–0.06

mm (0.0079

+0.0016

–0.0024

in)

Exhaust

0.35

±

0.05 mm (0.0138

±

0.0020 in)

8) If necessary, adjust the valve clearance. <Ref. to

ME(w/o STI)-28, ADJUSTMENT, Valve Clear-

ance.>

9) After inspection, install the related parts in the

reverse order of removal.
NOTE:

• Refer to “Camshaft” when installing the rocker

cover. <Ref. to ME(w/o STI)-61, INSTALLATION,

Camshaft.>

• Use a new clamp for the PCV hose (A), fit the cut

out in the ST with the protrusion on the clamp as

shown in the figure, and lock the clamp.

ST 18353AA000 CLAMP PLIERS

ME-04958

(A)

ME-04374

ST

ME-05976

(A)

(A)

ME(w/o STI)-28

Valve Clearance

MECHANICAL

Tightening torque:

6.4 N·m (0.7 kgf-m, 4.7 ft-lb)

B: ADJUSTMENT

1) Measure all the valve clearances. <Ref. to

ME(w/o STI)-25, INSPECTION, Valve Clearance.>
NOTE:

Record the measured value of each valve clear-

ance.

2) Remove the camshaft. <Ref. to ME(w/o STI)-59,

REMOVAL, Camshaft.>

3) Remove the valve lifter.

4) Measure the thickness of valve lifter using mi-

crometer.

5) Select a valve lifter of suitable thickness using

the measured valve clearance and valve lifter thick-

ness, and install it.
NOTE:

Use a new valve lifter.

6) Install the camshaft. <Ref. to ME(w/o STI)-61,

INSTALLATION, Camshaft.>

7) Install the cam sprocket. <Ref. to ME(w/o STI)-

57, INSTALLATION, Cam Sprocket.>

8) Install the timing belt. <Ref. to ME(w/o STI)-51,

TIMING BELT, INSTALLATION, Timing Belt.>

9) Measure all valves for valve clearance again at

this time. If the valve clearance is not within the ad-

justment value, repeat the procedure over again

from step 2).
Valve clearance (adjustment value):

Intake

0.20

+0.01

–0.03

mm (0.0079

+0.0004

–0.0012

in)

Exhaust

0.35

±

0.02 mm (0.0138

±

0.0008 in)

10) After adjustment, install the related parts in the

reverse order of removal.

ME-04966

ME-04653

ME-00024

Unit: mm (in)

Intake valve: S = (V + T) – 0.19 (0.0075)
Exhaust valve: S = (V + T) – 0.35 (0.0138)
S: Valve lifter thickness required
V: Measured valve clearance
T: Valve lifter thickness to be used

ME-00025