an annular body including a crown portion defining a longitudinal axis, a radial direction perpendicular to the longitudinal axis, a plane containing the longitudinal axis and the radial direction, and a contoured combustion bowl;

wherein in the plane containing the longitudinal axis and the radial direction, the contoured combustion bowl is radially surrounded by an annular cooling gallery that defines a maximum annular radial width, the contoured combustion bowl has a swirl pocket including a cylindrical surface defining a minimum diameter of the swirl pocket radially proximate to the maximum annular radial width of the annular cooling gallery, and a ratio of the minimum diameter to the maximum annular radial width ranges from 6.3 to 7.7; and

wherein the swirl pocket further includes a conical diverging surface extending radially outwardly, and axially upwardly from the cylindrical surface of the swirl pocket, and the annular cooling gallery further includes a conical surface that is radially proximate to the conical diverging surface, and that is parallel to the conical diverging surface.