This oil pump pressure relief valve and plug is specifically designed for the Citroën 11CV with a Perfo engine. This set is essential for regulating oil pressure within the engine and ensures that the oil circulates properly, which is crucial for the correct functioning of the engine. The 1/8 inch plug seals the opening, allowing the pump to operate under the right pressure. These components contribute to the reliability and efficiency of the classic vehicle's engine, ensuring the oil system functions properly.