Engine Overhaul 

An overhauled engine is an engine which has been removed, disassembled (torn down), cleaned, inspected,
repaired as necessary and tested using factory service manual approved procedures.
The procedure generally involves honing, new piston rings,  bearings,  gaskets, oil seals.
When done by a competent engine builder the engine will perform as new.
The engine may be overhauled to 'new limits' or 'service limits', or a combination of the two using used parts, new  original equipment manufacturer 
(OEM) parts, or new aftermarket parts.
The engine's previous operating history is maintained and it is returned with zero hours since major overhaul.