Patent ID: 7536988

Claim:
A cylinder head comprising: a lifter guide boss part defining a lifter bore configured and arranged to slidably support a valve lifter that is periodically pushed down by a cam that rotates in accordance with a rotation of a camshaft; a concave relief groove portion having a predetermined width and a predetermined depth formed on the lifter guide boss part in a position corresponding to a rotation direction of the cam to avoid an interference between the cam and the lifter guide boss part due to a rotation of the cam, the relief groove portion including a pair of groove side surfaces extending substantially parallel to a rotation plane of the cam and a groove bottom surface extending between the groove side surfaces with a pair of corner sections being formed between the groove bottom surface and the groove side surfaces; and a guide portion protruding from the groove bottom surface of the relief groove portion in a sliding direction of the valve lifter to slidably guide the valve lifter, the guide portion being spaced apart from the corner sections of the relief groove portion.