Engine and method for improved crankcase fatigue strength with fracture-split main bearing caps

An internal combustion engine comprising:

• a cylinder block cast and machined with a plurality of crankshaft bearing caps as a single one-piece assembly to include:
• a pair of generally parallel longitudinally extending sidewalls defining a lower crankcase therebetween;
• a plurality of longitudinally spaced laterally extending web walls, with each web wall having an upper portion attached to the pair of sidewalls by a lateral connector, and a lower portion;
• and
• a plurality of crankshaft bearing bores aligned on a crankshaft bore axis and extending through the lower portion of each of the web walls;
• wherein the crankshaft bore axis is disposed on a horizontal plane bisecting the crankshaft bearing bores and extending between the sidewalls;
• wherein the lower crankcase extends upward beyond the horizontal plane;
• and
• a plurality of blend radii, with each blend radii connecting the upper portion of one of the web walls with one of the lateral connectors;
• wherein the plurality of bearing caps are fracture split from each of the web walls along a downwardly sloping fracture-split line initiated at opposite sides of the crankshaft bearing bores on the horizontal plane, and extending downward at a predetermined angle to outer edges of the bearing caps disposed below the horizontal plane to increase the radius of each of the blend radii;
• and
• wherein each of the blend radii extend from a location at the outer edge of one of the bearing caps disposed below the horizontal plane to the adjacent lateral connector disposed above the horizontal plane.