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The scope of the study is limited to the period of closing valve, but phenomena existing in the antecedent phase influence conditions in the contact between seats. Friction type in such contact varies from mixed to boundary or even dry one, depending on the amount of oil and wear debris wherein. The operational conditions for inlet and outlet valve are different because of temperature in contact and deposition of carbon deposits. The complexity the phenomena in contact zone, including valve rotation makes difficult the modeling of friction. The valve rotation is considered only in macro scale and the other displacements of seats in micro and macro scale. The initial shape of seats resulted from grinding and lapping process varies during impacting and abrasion wear.