In an internal combustion engine, the cylinder head rests on the top of the cylinder block. One of the parts of head assembly is the valve guide, which is used to orient the valves correctly. Typically valve guide is made up of cast iron and fitted in cylinder head with the use of interference fit. The study aims to find the stress developed due to interference fit in valve guide and cylinder head of air cooled diesel engine. This is done using 3D simulation model and FEA. The investigation aims to provide the design intent to resolve valve guide loosing issue in operating temperature ranges.