Material behavior depends on average peak temperature, stress magnitude and stress gradient. This assumption is valid since temperatures varies slowly when compared to pressure (stress). In this paper, a RR Merlin head is simulated with a few mathematical models used in Formula 1 racing. These extremely simplified models make it possible to evaluate temperatures and pressures starting from very few data. The method is described in detail, along with the many experimental coefficients available from several years of design activity. A step by step approach is used to allow the comprehension of this method that was developed by the Authors. The choice of the RR Merlin was dictated by the public availability of experimental data on temperatures. In fact, in the case of the RR Merlin XX, very reliable experimental results are available in NACA TN 2069. A reverse engineering process was applied on a rescued RR Merlin XX head. An accurate redesign was performed to obtain a 3D model. Assembly instructions and tolerances were found on original Rolls Royce overhaul manuals. In this way assembly and working loads were calculated and simulated. Nonlinear FEA analysis was performed on this CAD model with extremely satisfactory results for the thermal loads. Well known criticalities of the original design were found. The results were compared with NACA results both for heat rejection and temperatures. However, the mechanical stresses proved to be more critical for simulation and evaluation. Therefore, they will be discussed in another, dedicated paper.