PURPOSE: To facilitate to pressingly insert, mount and dismount the both in such a way that cooling water ports and oil port between a cylinder head and a crankcase are coupled by means of pipes, and O rings are interposed on the outer periphery of the pipes.

CONSTITUTION: A metal packing 19 is interposed at the junction face between a cylinder head 1 and a crankcase 5. A valve rod chamber 4 which communicates to respectively cooling water ports 13, 17 and an oil port 18, and in addition, has a valve rod 3 inserted is formed between the both. And, pipes 11, 12 are inserted to each port and the valve rod chamber, O-rings 15, 16 are provided on the outer periphery, which pressingly inserted by means of the cylinder head 1 and the crankcase 5.