Engine cylinder head having an improved intake port configuration, and engine incorporating same

In an internal combustion engine of the type having a combustion chamber formed therein and including:

• a cylinder head with an intake opening formed therein for delivering an intake mixture to the combustion chamber, said cylinder head also having an intake port formed therein which communicates with the intake opening;
• an intake valve which has a valve stem and which is operable to open and close the intake opening of the combustion chamber;
• and
• a valve guide which slidably supports the valve stem therein;
• wherein the improvement comprises an improved configuration of said cylinder head comprising an improved intake port configuration in said cylinder head, wherein said intake port is curved in shape and leads from a hole formed in a side portion of the cylinder head to the intake opening of the combustion chamber;
• wherein the valve guide is fixed to the cylinder head at an intermediate location on a curved wall of the curved intake port,
• wherein a passage cross-sectional area of the intake port reduces with an increasing distance from the intake opening of the combustion chamber in a region of the intake port adjacent to the intake opening of the combustion chamber, and
• wherein the passage cross-sectional area, at a location which is spaced approximately 10% of a total length of the intake port from an opening thereof at the combustion chamber, is less than or equal to 0.8 times an area of the intake port at the intake opening of the combustion chamber.