Subaru IMPREZA GD 2007 Series Manual page 2453

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MECHANICAL
7) Make sure that the cam and crank sprockets are
positioned properly.
CAUTION:
• Intake and exhaust camshafts for this DOHC
engine can be independently rotated with the
timing belts removed. As can be seen from the
figure, if the intake and exhaust valves are lifted
simultaneously, the valve heads will interfere
with each other, resulting in bent valves.
(A) Intake camshaft
(B) Exhaust camshaft
• When the timing belts are not installed, four
camshafts are held at the "zero-lift" position,
where all cams on camshafts do not push the
intake and exhaust valves down. (Under this
condition, all valves remain unlifted.)
• When the camshafts are rotated to install the
timing belts, #2 intake and #4 exhaust cam of
camshafts (LH) are held to push their corre-
sponding valves down. (Under this condition,
these valves are held lifted.) Right-side cam-
shafts are held so that their cams do not push
valves down.
• Camshafts (LH) must be rotated from the
zero-lift position to the position where the tim-
ing belt is to be installed with the smallest pos-
sible angle, in order to prevent mutual
interference of intake and exhaust valve heads.
Timing Belt
• Do not allow the camshafts to rotate in the di-
rection shown in the upper figure. Doing this
may cause both the intake and exhaust valves
to lift simultaneously, resulting in mutual inter-
ference of heads.
(A)
(B)
ME-00086
ME(H4DOTC)-52
(A)
(A)
(B)
(A)
(A)
(B)
(A) Direction of rotation
(B) Timing belt installation position
ME-03177