The fuel properties put great impact on engine performance. Therefore, the adaptation of an alternative fuel to the existing engine may require some of the design modifications in order to have superior or almost identical performance. India is the largest producer of castor oil and it is the least explored feedstock to be used as alternative fuel in the form of biodiesel. Castor biodiesel has the highest viscosity amongst all the previously explored biodiesel sources. This study was conducted to investigate the effects of varying fuel injection timing and fuel injection pressure on single cylinder C.I. engine fuelled with 20% blend of castor biodiesel in diesel. A comprehensive comparative analysis has been made based on various combustion, performance and emission parameters. Results showed that 20% blend of castor biodiesel in diesel can be used without any alteration in fuel injection system.