Oracle 7.3.2.3 import performance

I need to improve the time it takes to import data from 7.1.6 to 7.3.2.3 Oracle on a Dynix/ptx platform. At present it is taking about 26 hours. The job must be done using tape as there is a space restriction on the servers disks. We have tried adjusting one or two of the parameter file settings but are now running out of time for experimentation as our new application, which only runs on 7.3.2.3, must be up and running by the 16th March.

    Can anyone help please?

                                            Alan