Cylinder head construction

A cylinder head construction comprising:

• a mating surface for connection to a cylinder block;
• an inner surface having a large-radius of curvature wall portion and a small-radius of curvature wall portion and defining a multi-hemispheric combustion chamber, said large-radius of curvature wall portion having an intake port through which an air-fuel mixture enters said combustion chamber, and said small-radius of curvature wall portion having an exhaust port through which gases produced by combustion of said mixture leave said combustion chamber;
• ignition means in said cylinder head for igniting said mixture in said combustion chamber;
• an intake valve in said intake port actuable to selectively open and close said intake port and an exhaust valve in said exhaust port actuable to selectively open and close said exhaust port, said intake port and exhaust port having therein valve seats on which said intake valve and exhaust valve are seated;
• and
• guide wall means extending from said inner surface of said cylinder head towards said mating surface and having a first wall surface which faces said intake port and is generally cylindrical around the central axis of said intake port, a second wall surface which faces said exhaust port and curving outwardly from said exhaust port and which is generally smoothly connected with said small-radius of curvature wall portion of said inner surface and extending toward said mating surface in a downward slope to form a junction with a portion of said first wall surface, and a third wall surface which is at the level of said mating surface, said junction being a smooth continuation of the line of junction of said large-radius and small-radius of curvature wall portions, said first wall surface being radially spaced from the outer periphery of said intake valve a distance of from 1 to 4 mm, and having a height in a direction parallel to a line along which said intake valve moves which is greater than the maximum lift of said intake valve, and the downward slope of said junction defining a width of said first wall surface in a direction normal to said line and along said outer periphery of said intake valve which gradually decreases in the direction of movement of said intake valve as it opens said intake port.