The objective of this paper is to develop a robust methodology to study the internal combustion (IC) engine block vibrations and to quantify the contribution of combustion pressure loads and inertial loads (mechanical loads) to the engine block vibrations. This study is not extended to the sound pressure generated by the engine and contribution analysis for that response. In an IC engine, the combustion and mechanical/inertial loads are the main sources of engine block vibrations. They both contain not only strong harmonic content due to their repetitive nature but also transient broadband impact loads. Therefore, it is difficult to identify/separate the contribution of combustion and inertial loads in the vibration response due to their correlated frequency excitations. One of the tools utilized in the industry to separate the combustion and mechanical noise is the Wiener filter. This study uses the Wiener filter to separate and understand the combustion and mechanical noise contributions in conjunction with the block vibration. The Wiener filter was built using only the dynamic part of the combustion pressure signal and of the engine block vibration response by removing the harmonic content. The dynamic of portion of their respective raw signals is termed as residue. The Wiener filter was then multiplied by the raw cylinder pressure signals to obtain the vibration of the engine block due to the combustion contribution without the influence of harmonics present in signal. Engine vibration due to the mechanical sources was then obtained using the difference of the raw block vibration and of the vibration due to combustion. Finally, this paper demonstrates the process of developing Wiener filter for a three-cylinder IC engine and of identifying the partial contribution of combustion and mechanical excitation in the overall vibration response on an IC engine block.