Subaru 2009 IMPREZA Service Manual page 1112

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7) Make sure that the cam and crank sprockets are

positioned properly.

• 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 are not pushing

down on the intake and exhaust valves. (Under

this condition, all valves remain unlifted.)

• When the camshafts are rotated to install the

timing belts, #2 intake and #4 exhaust cam of

camshaft LH are held, pushing their corre-

sponding valves down. (Under this condition,

these valves are held lifted.) Camshaft RH are

held so that their cams do not push the valves

• Camshafts LH must be rotated from the zero-

lift position to the position where the timing belt

is to be installed with the smallest possible an-

gle, in order to prevent mutual interference of

intake and exhaust valve heads.

ME(H4DOTC)-54

• 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 valve heads.

(A) Direction of rotation

(B) Timing belt installation position