This paper deals with the Coupled thermo mechanical analysis of a cylinder head, cylinder block and crank case with the liner of an uprated engine. The existing engine develops 780 hp output with mechanical driven supercharger and the engine is uprated to 1000 hp by replacing the supercharger with a turbocharger and new Fuel injection equipment. For uprating any engine, the piston and cylinder head are the most vulnerable members due to increased mechanical and thermal loadings. Mechanical loading is due to the gas pressure in the gas chamber and its magnitude can be judged in terms of peak pressure. Thermal loading is due to temperature and the heat transfer conditions in the piston surface, cylinder liner and the cylinder head. The relative importance of the various loads applied on the head and cylinder block in operation are assessed and a method of predicting their influence on the structural integrity of the components described.The Cylinder head, cylinder block and crank case of the uprated Engine have been modeled using finite element method and coupled steady state heat transfer cum thermal stress analysis has been done. The present study concentrates on the peak conditions such as peak firing pressure and steady state thermal conditions. This study shows that the cylinder head and cylinder block can withstand the higher stresses due to enhanced pressure and thermal loads in the uprated version of the engine and no further design modifications are necessary. And it is also observed from the successful completion of Endurance and Performance evaluation of this uprated engine in the test bed, as well as in the vehicle.