This paper presents the design, structural analysis, and risk assessment done by Cummins to evaluate the structural integrity of Light Duty engine cylinder head for a Medium Wheelbase (MWB) pick-up truck. Initially, Cummins used F2.5L (4-cylinder) engine that has 154hp, but rising market demands for more power, fuel efficiency, lower cost and weight, and future emission compliance led to customer requirements for 177hp (Drive New F2.5L, 15% uprate) and 197hp+ (Drive New F3.0L, 22% uprate) from the same base engine. The increase in power requirement possesses challenges on critical components, especially cylinder heads in terms of thermal and structural limits. This paper addresses the challenges and risks in current cylinder head design driven by new power demands, specifically reduced fatigue margins in the water jacket area and increased temperatures on the combustion face under high thermomechanical loads. It explores the design modifications made to the cylinder head design to enhance stiffness, all within a constrained space claim. Multiple analysis led design iterations were performed using cutting edge CAE software such as Ansys, Dassault Systems fe-safe, and PTC Creo to ensure the structural integrity of the cylinder head under high thermal and mechanical loads, and to keep design margins within acceptable limits. A key feature identified through topology optimization was diagonal ribbing pattern on each cylinder, which is novel (NUD) and similar pattern can be applied to both new and existing engine platforms to enhance stiffness without major changes to the water jacket. The Cylinder head was subjected to long endurance test, which comprises of high thermal and mechanical loads under extreme operating conditions. After running for around 800+ hours, the engine was stopped for magnetic particle inspection for any signs of fatigue failure. No cracks were observed on the F3.0L engine. However few cracks were observed on the F2.5L cylinder head combustion face at Exhaust & intake bridges. Upon investigation, it was concluded that crack was due to high thermo-mechanical fatigue loads, and hence, needed further optimization on the cylinder head. Furthermore, cylinder head gasket coolant orifice optimization is done to improve the coolant distribution to each cylinder. Thermal analysis showed reduction in exhaust & intake bridge temperature within the acceptable limits. This paper captures the detailed study to resolve head thermal fatigue crack failure on F2.5 L Diesel engine.