You do not check valve timing by seeing how far left/right the cam tower index marks are....you turn the engine over by hand at the crank [ in normal rotation direction, of course] until the cam index marks are perfectly aligned.
Then you go down and read the degrees on the crank timing index scale. That tells you how far off you are in degrees ..you then 1/2 that for offset spec....but first see how far off you are ..if it is not many, it is not worth the bother.

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A Dalton