Engine overhaul. An overhauled O-360 will cost close to $20k
installed, with a TBO of 2000 hrs, so this is $10/hr. Even if you do
not save an overhaul resever, your plane will depreciate at roughly
half this value ($5/hr) because of the increased engine time.

And this is where you see a large difference for you Lyc boys. Lyc
prices are ridiculous. I can have my O-470 overhauled and reinstalled
for closer to $15K. I will be turning my 470 into a 520 and it will
still be less than $20K installed.