| 摘要 |
PURPOSE:To enhance the cooling efficiency of ignition plugs in an engine having intake and exhaust valves two in each per engine cylinder, by forming an inclined spark-plug fitting hole between two exhaust ports in a cylinder head, and by forming cooling water drill holes in the vicinity of this fitting hole. CONSTITUTION:In an engine in which intake and exhaust ports 17, 18 two in each are formed in a cylinder head 13 and the opening sections of the ports 17, 18 on the combustion chamber 16 side are closed by intake and exhaust valves 19, 20, an inclined spark-plug fitting hole 36 is formed in the cylinder head 36 between the two exhaust ports 18, crossing the exhaust valve 20. The fitting hole 36 is opened at its front end 36 to the center of top section of the combustion chamber 16. Further, two drill holes 42 are formed crossing each other and extending through the lower deck 38 from cooling water inlet ports 41 formed in the lower deck 38 of the cylinder head 16 at positions below the exhaust ports 18 to a water jacket 40. |
