2.3 is 89.6 bore x 91 stroke

8.96 / 2 = 4.48 so (4.48x4.48) x 3.142 = 63.061 cm2
63.061 x 9.1 = 573.857 cc x 4 = 2295.4cc

You would need a bore of 93.6mm to get out to 2.500cc

9.36/2 = 4.68 so (4.68x4.68) x 3.142 = 68.817 cm2
68.817 x 9.1 = 626.237 x 4 = 2505cc

2.3 has the same bore centres as the 2 litre and there is not a lot material left for boring out.

Brave decision !