Small diesel engines are used for commercial transportation for rural and urban area due to cost and efficiency aspect. They are also the reason for pollution because of various reasons. This study aims to examine the effect of intake valve lift, timing and duration on four-stroke single-cylinder diesel engine’s volumetric efficiency. One-dimensional thermodynamic simulation analysis is carried out for gas exchange and performance improvement study with various intake valve lifts, timing and duration along with swirl variation strategies. 1D simulation model is validated within 5% band with respect to engine’s testing data. Early inlet valve opening (EIVO), closing (IVC) effect along with lift options are analyzed on engine’s volumetric efficiency. IVO timings are varied from 31˚bTDC to 5˚aBDC with an interval of 6˚CA with duration varied from 50˚ HCE to 70˚ HCE with three lift options. Cylinder head swirl is reduced by 25%, while flow coefficient is improved by 10%. This along with optimum timing and lift combination produce 5–15% improvement in volumetric efficiency at wide engine speed range in simulation. Higher lifts, wide duration and lower lift with duration is beneficial for rated and intermediate engine speeds, respectively. © TJPRC Pvt. Ltd.