A method of improving corrosion resistance of a cylinder cover including a port that is an intake port or an exhaust port. The cylinder cover is configured such that an annular cooling water passage is formed between an inner peripheral surface of the port and a valve seat ring when the valve seat ring is inserted in the port. The method includes forming a weld overlay layer on each of sealed regions of the inner peripheral surface of the port by laser metal deposition using a welding material made of a nickel-based alloy, a copper alloy, stainless steel, or a titanium alloy, the sealed regions being positioned at both sides of the cooling water passage, respectively.

An engine cooling device includes a heater circulation passage including an exhaust-side channel and a heater channel, the exhaust-side channel extending through an exhaust port-side portion of a cylinder head, the heater channel extending through a heater core; an auxiliary device circulation passage including a main channel and an auxiliary device channel, the main channel extending through a portion of the cylinder head other than the exhaust port-side portion, the auxiliary device channel extending through an auxiliary device; a temperature detecting portion configured to detect a temperature of an engine; and a channel switching valve configured to perform connection between the main channel and the auxiliary device channel and connection between the heater circulation passage and the auxiliary device circulation passage depending on the detected temperature falling within one of three temperature ranges.

A cylinder block assembly may include a cylinder block, a cylinder body disposed in the cylinder block, with a plurality of cylinder bores formed in the cylinder body, a fluid jacket, which is formed between an inner circumferential surface of the cylinder block and an outer circumferential surface of the cylinder body, and through which coolant flows, and a block insert disposed in the water jacket and configured to guide a flow of coolant, wherein the cylinder block may include a second block coolant outlet, which is formed at a second side in a surface of an exhaust side of the cylinder block, and through which the coolant in the water jacket is discharged, and wherein the exhaust side may include a side at which combustion gas is exhausted out of the cylinder body.

In an internal combustion engine, the cylinder block includes a first blowby gas passage and a first oil return passage. The cylinder head includes a second blowby gas passage connecting the first blowby gas passage with a connection passage connected with a gas-liquid separator, an oil return chamber separated from a valve operating chamber and the second blowby gas passage by first and second partition walls, respectively, and provided with a first oil return hole connected with the gas-liquid separator, and a second oil return passage connecting the valve operating chamber with the first oil return passage. The first partition wall is formed with a second oil return hole connecting the oil return chamber with the valve operating chamber. The second partition wall is formed with a ventilation hole connecting the oil return chamber with the second blowby gas passage at a higher position than the second oil return hole.

In an internal combustion engine, the cylinder block includes a first blowby gas passage and a first oil return passage. The cylinder head includes a second blowby gas passage connecting the first blowby gas passage with a connection passage connected with a gas-liquid separator, an oil return chamber separated from a valve operating chamber and the second blowby gas passage by first and second partition walls, respectively, and provided with a first oil return hole connected with the gas-liquid separator, and a second oil return passage connecting the valve operating chamber with the first oil return passage. The first partition wall is formed with a second oil return hole connecting the oil return chamber with the valve operating chamber. The second partition wall is formed with a ventilation hole connecting the oil return chamber with the second blowby gas passage at a higher position than the second oil return hole.

A method of improving corrosion resistance of a cylinder cover including a port that is an intake port or an exhaust port. The cylinder cover is configured such that an annular cooling water passage is formed between an inner peripheral surface of the port and a valve seat ring when the valve seat ring is inserted in the port. The method includes forming a weld overlay layer on each of sealed regions of the inner peripheral surface of the port by laser metal deposition using a welding material made of a nickel-based alloy, a copper alloy, stainless steel, or a titanium alloy, the sealed regions being positioned at both sides of the cooling water passage, respectively.

A method of improving corrosion resistance of a cylinder cover including a port that is an intake port or an exhaust port. The cylinder cover is configured such that an annular cooling water passage is formed between an inner peripheral surface of the port and a valve seat ring when the valve seat ring is inserted in the port. The method includes forming a weld overlay layer on each of sealed regions of the inner peripheral surface of the port by laser metal deposition using a welding material made of a nickel-based alloy, a copper alloy, stainless steel, or a titanium alloy, the sealed regions being positioned at both sides of the cooling water passage, respectively.

A cylinder head containing an exhaust system manifold for an engine includes screw holes formed through a fastening face of the cylinder head and an exhaust pipe, and outlet cooling channels that are provided adjacent to an outlet of a confluence of the manifold, and are disposed between the screw holes and the outlet. Coolant flows through the outlet cooling channels.

A cylinder head containing an exhaust system manifold for an engine includes screw holes formed through a fastening face of the cylinder head and an exhaust pipe, and outlet cooling channels that are provided adjacent to an outlet of a confluence of the manifold, and are disposed between the screw holes and the outlet. Coolant flows through the outlet cooling channels.

An engine cooling system for cooling a cylinder head and a cylinder block separately may include a cylinder block having cylinders arranged from a front side to a rear side of an engine with a block water jacket formed therein around the cylinders, a cylinder head fastened to a top side of the cylinder block with a head water jacket formed therein from the front side to the rear side of the engine, a water pump mounted to a front side of the cylinder block for pumping coolant to a front of the block water jacket, and a coolant control valve arranged in a rear side of the cylinder block and the cylinder head to have a first end connected to a rear end of the block water jacket and a second end connected to a rear end of the head water jacket for having the coolant supplied thereto.