| 摘要 |
PROBLEM TO BE SOLVED: To close the oil hole of a cylinder head facing a valve mounting hole having an arcuate opening airtightly. SOLUTION: The masking rubber 58 of a masking holder body 1 inserted into the valve mounting hole 53A of a cylinder head 51W is provided with masking, rubber retaining parts 15, 19 large enough to cover arcuate openings W1, W2 provided at the valve mounting hole 53A. Even if leak test of an oil hole 52 is performed by supplying compressed air into the masking rubber 58, the masking rubber 58 is prevented from expanding to project from the openings W1, W2 by means of the masking rubber retaining parts 15, 19. Consequently, the oil hole facing the valve mounting hole 53A is closed surely and airtightly.
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