There are a few reasons for a cylinder wall to become smooth so that oil
isnít contained in the cross hatching and blowby goes up, oil
temp goes up, oil gets black quickly and oil consumption
First is cylinder wall glazing, that is actually unburned fuel
deposits coat the cylinder walls and eventually turn into something like a varnish
Itís from low temp operation, if the engine
is allowed to run at design temp this wonít happen, it takes very little load to get up to operating temp, but loads just from an alternator
if using the engine
to charge batteries
is often not enough load.
Often unless allowed to get really excessive glazing can be recovered from, by a good detergent in the oil and an Italian tune up.
Iíve never seen it so bad that the engine has to be honed myself, heard of it, but never seen it.
Second is bore polishing, something that airplanes that are infrequently used and our boats suffer from as they age. An engine that sits for a decent long interval, say weeks can and will form a light coat of rust on the cylinders, especially if it has water
in the exhaust
as that is a humid environment
When the engine is started of course this rust is very quickly cleaned off by the piston rings, but it causes wear of the cross hatching, repeat dozens or hundreds of times and eventually you have polished your bores.
Bore polishing the only cure is either honing, or usually bore it out to oversize as likely the engine is decades old anyway.
However these engines can have excellent crankshafts and cams, lifters etc. that exhibit very little wear, they are mostly victims of just not being used, and are often excellent candidates for an overhaul
I plan on keeping my old 4JH(B)E until lack of parts
force me to replace it, I think your crazy to not overhaul
an engine that still has good parts
availability, a good overhaul is Better than new, cause you determine the tolerances in an overhaul, the engine can be as perfect as you can make it if you desire.