Intake port structure in an internal combustion engine

An internal combustion engine having a cylinder head with a mounting surface, a combustion chamber, an intake port, an exhaust port, an intake valve seat mounted in said intake port at said combustion chamber, and an exhaust valve seat mounted in said exhaust port at said combustion chamber, wherein

• said intake port has an edge portion at an inner wall on a lower side immediately adjacent and upstream of said intake valve seat, an angle formed by a center line of said intake port with respect to said mounting surface being smaller than an angle formed by an end face of said exhaust valve seat with respect to said mounting surface, an extension of the center line of said intake port passing below an apex of said combustion chamber at a center of said combustion chamber and a distance H from said mounting surface to an intersection between an extension of the center line of said intake port and a straight line passing through said apex of said combustion chamber to intersect said deck surface at a right angle being related to a distance H.sub.0 from said deck surface to the apex of said combustion chamber such that H.sub.0 >H>2H.sub.0 /3.

An internal combustion engine having an overhead valve cylinder head with a combustion chamber, an intake port, an exhaust port, an intake valve seat in said intake port at said combustion chamber, and an exhaust valve seat mounted in said exhaust port at said combustion chamber wherein

• said intake port having a lower edge portion effective for causing vertical swirl in the combustion chamber, an angle formed between a center line of said intake port and an end face of said exhaust valve seat in a manner also effective for causing said vertical swirl, the center line of said intake port being oriented with respect to a roof of the combustion chamber in a manner also effective for causing said vertical swirl, and a distance H perpendicularly from deck surface of said cylinder head to an intersection between an extension of the center line of said intake port and a straight line passing through an apex of said combustion chamber to intersect said deck surface being related to a distance H.sub.0 perpendicular from said deck surface to the apex of said combustion chamber such that H.sub.0 >H>2H.sub.0 /3.