Originally Posted by
Fl1ingfrog
The difference between "rebuilt" or "overhauled" is not clear
Under FAA regulations, the difference is clear. An overhaul is when the engine is disassembled and reassembled, with work done in accordance with the manufacturers service instructions, including some specifics (Lycoming allows more flexibility than Continental) but otherwise all components must be measured and found within service limits, no better, before reassembly. The US government cannot in general force you to improve your engine beyond service limits, and it makes no difference that you have it pieces. Service limits are precisely that and if you want to, you can reassemble an engine as an overhaul after doing nothing except what's in the manufacturers service instructions, as long as wearing components are otherwise within service limits. This is why it's important to see the component level data for an overhauled engine when buying it, the FAA definition of overhaul doesn't actually tell a lot about what was done to improve the condition of an overhauled engine while it was apart.
A rebuild is something different - in addition to compliance with the manufacturers service instructions for an overhaul, the engines components must be within the limits documented by the engine manufacturer for a
new engine, and the work can only be called a rebuild when performed by an authorized shop, typically the manufacturer, not any A&P mechanic like an overhaul.
That said, I agree that if it's a 'first run' engine (never overhauled) it may be a very good idea to have it overhauled locally and consider the condition of each component individually. For example, if some part is barely outside of new limits after 2000 hrs, and so very well within service limits, do you really want to replace it instead of reinstalling it and seeing how it looks again after 4000 total hrs?