that comes in contact with the connecting section 3 d 25 gt d 20 therefore when assembled in the engine by bringing the base end section of the valve stem 20 in contact between the protrusions 25 in the middle section in the lengthwise direction of the connecting section 3 it is possible for the base end section of the valve stem 20 to fit with the connecting section 3 such that it can rock and move freely and such that it is possible to keep it from moving to the sides in the width direction of the connecting section 3 up and down direction in fig1 front and back direction in fig1 and left and right direction in fig1 this work of forming protrusions 25 in order to regulate the inner dimension in width direction of the fitting section with the valve stem 20 can be performed mainly by swaging the metal plate to cause residual compression stress to occur as is well known the residual compression stress is not related to damage such as cracking but functions to suppress the occurrence of damage such as cracking therefore by processing the protrusions 25 it is possible to prevent damage such as cracking from occurring in and near these protrusions 25 next fig1 is used to show a fifth example of the embodiment of the invention in the case of the first example described above the protrusions 25 were formed nearly along the entire height of the guide wall sections 21 however in this example the protrusions 25.