There is no set compression reading for a rebored engine as it largely depends on the specific engine model and type of piston used. However, the compression reading on a 1.4L Opel Corsa engine with a 1000 rebore should be around 150-180 PSI per cylinder. This reading can vary slightly depending on engine condition, altitude and other factors. It is important to refer to the manufacturer's specifications for compression readings for your specific engine model.