Biodiesels are renewable fuels and their usage in diesel engine can decrease the dependence on fossil-based fuels which are exhaustive in nature. Further they can effectively address the alarming increase in emission levels in the atmosphere and provide savings in the foreign exchange. The present work mainly focuses on the effect of swirl techniques adopted on the performance of the modified diesel engine powered with two B20 based biodiesels derived from Ceiba Pentandra (CPNTOME B20) and Nigella Sativa (NIZSAOME B20) respectively. The swirl techniques are adopted by suitable modifications on both the piston and cylinder head surfaces respectively. Optimized number of cavities on piston and cavities and domes on the cylinder head improved the diesel engine performance powered with selected biodiesel blended fuels. Accordingly, 6 number of cavities on the piston and 2 domes and 3 cavities on the cylinder head surfaces provided higher brake thermal break efficiency (BTE), lower hydrocarbons (HC), carbon monoxide (CO), smoke emissions while nitric oxide (NOx) emissions were increased for the diesel engine powered with two B20 blends compared to other swirl combinations used. Among the two biodiesels used CPNTOME B20 showed higher engine performance compared to NIZSAOME B20. BTE of engine fuelled with diesel increased by 4.86% and 6.54% respectively when compared with B20 blends of CPNTOME and NIZSAOME. Smoke emissions of engine fuelled with diesel decreased by 8.27% and 11.43% respectively when compared with B20 blends of CPNTOME and NIZSAOME.