To make a 2.5L

[TurboGalant]

How much will have to be bored out and what size pistons will I have to buy to make the 4g64 a 2.5L engine?

[94es24]

you will need a bore of about 89mm

[hyer717]

Hmmm, might want to check and see how much cylinder wall you would have left, might be getting a little thin...??? Could cause overheating problems if your walls are too thin. Just my $.02

[fstrthnu]

You can only safely bore out the '64 0.020 over. I don't know how much extra displacement that would give you though.