Maintaining high aircraft’s propulsion system reliability requires a good knowledge of engine’s heat transfer conditions at each engine running time. Even though the flow around the cylinder may be steady, the heat flux from the engine is not evenly distributed. This is caused by varied engine head and fins geometry and uneven heat transfer coefficient distribution. The lack of knowledge of the local heat transfer coefficient values and time coefficients for the transient heat transfer make it unfeasible to make an analytical model for a given geometry. One transient Computational Fluid Dynamics simulation does not solve the heat transfer fully. Only a conjugate simulation allows an in-depth analysis of a transient heat transfer. The Combustion and species transport fluid simulation is coupled to the temperature field solid simulation. This work presents the methods and results of such conjugate heat transfer simulation. The change of heat flux parameters in respect to time is shown. The results are verified by the real engine measurements.