maximum u can bore it out too

so yer the question is simple how much bigger can i make it, standard 2.25 petrol atm ex military but not 24 volt

why?

cus i have one that needs rebuilding and if im gonna do it i want bore it out to the max and see how many hp i can get this thing to turn out

hi, I am getting too old for playing with engines but with the land rover block, keep to stock piston sizes for reliability and cost, then spend money getting the whole bottom end balanced, dynamically and static. take a little off the flywheel, don't forget the clutch as well. that will make a smooth engine that will more than compensate for the notional loss of a fraction of a HP due to losing a few cc's.
increase the compression ratio of the head a bit, 9.5:1 about max. I know my mate has just gone to 10.5:1 and i am waiting to say "told You!".
if you haven't gas flowed heads get one off the shelf exchange, get a high lift cam, and then go for a SU carb conversion for simplicity. (look up ACR for kits). renew the dizzy so that the timing isnt erratic. etc etc
This will set you back about £1900,If you get it done yourself, and that is why i tend to stick with standard now!
if i only did one thing to a block it would be the balancing the bottom end and lightening the flywheel.
building engines can lead to divorce when she finds out how much you have spent!
have fun.