PURPOSE: To improve the combustion efficiency by performing large beveling work only at two points on the opening edge of a suction port to form a suction gas guide thereby producing strong disturbed state in the cylinder.

CONSTITUTION: Large beveling work is performed only at two points on the suction port open edge 10 on the lower face 8 of a cylinder head 7 to form two suction gas guide grooves 11, 12. The suction flow flowing in along the groove 11 will swirl (S) around the axis of cylinder. The suction gas flow along the groove 12 will be straight drop flow (L). Both suction flows will collide in the cylinder 14 to produce strong disturbed state in the cylinder 14. Consequently the combustion efficiency of a direct injection engine can be improved.