You can get things called Stroker Kits which supply you with parts to give your car bigger displacement. You can make a (B-series) 1.6 into 1.8, 1.8 into 2.0, (H-series) 2.2 into up to 2.5 I think.

Think of it as using a giant drill bit to drill the piston hole bigger. You can only "drill" it out so much before it rips apart, so think of it like that when thinking how much you can bore a car out to. 1.8 to 5.8 would have bored the whole block into a fine powder.