Internal combustion engine having a concave piston cooperating with a convex squish surface on the cylinder head

The engine has a central combustion cavity (44) that is placed in an upper side of a piston (16). The upper side has an annular peripheral zone (48) with tapered concave shape in order to be inclined towards the cavity. A cylinder head (18) has a chase surface which has tapered convex shape that is complimentary to a peripheral zone of the piston for cooperating with the zone of the piston.