If the purpose of the rebuild is to bring the engine back (or as close as feasibly possible) to its original performance, what are some things that should always be replaced?
This obviously depends on the condition of the engine, so let's say a 300,000 km engine which has had regular oil changes its whole life.
Gaskets, seals, belts, bolts, etc. yes you should replace, but how about components such as valves, valve springs / hydraulics, piston heads, connecting rods, camshafts, piston rings to name a few?
When it comes to replacing parts or touching up your engine, there are several terms you'll hear a lot. Words like overhaul, rebuild, remanufacture, and refurbish may come up after a few years when parts of your engine require maintenance or replacement. Knowing the differences between an engine overhaul and rebuild will make your next big project more manageable and help you decide where to direct your focus.
An engine rebuild is typically what it sounds like, rebuilding the engine. Typically, engine rebuilds require using new parts and focusing on bringing your engine to an almost pristine condition. Many of the parts you replace in an engine rebuild are also part of a complete overhaul. A notable difference between a rebuilt and remanufactured engine is that the latter must use new parts from the original equipment manufacturer, so it's a rebuild without relying on aftermarket parts.
Engine overhauls are typically associated more with maintenance than rebuilding an engine. There are two different types of overhauls, in-frame and out-of-frame. In-frame overhaul kits allow you to swap out parts and vital components without removing the engine from the block, while complete overhaul (out-of-frame) kits require taking out the engine. Both kits contain essential diesel engine parts like pistons, rings, gasket sets, bearings, and washers. Most out-of-frame kits include front and rear seals as well.
When looking at the differences between an engine overhaul and a rebuild, you may wonder which one you need. Both rebuilds and out-of-frame overhauls are lengthy and expensive processes that require taking the engine out of the block. An engine rebuild is often the better option when you're planning to replace everything to get your current engine to as clean of a slate as possible. Overhauls are good when you need to update specific parts or pieces to keep things running smoothly. The better choice may come down to the current state of your engine, but it's a good idea to have an in-frame overhaul kit around in case you need to make some modifications.
To learn more about diesel auto parts and engine overhaul kits, ATL Diesel has everything you need. We have parts for heavy-duty engines, overhaul kits for various engine types, and many helpful blogs covering everything you need to know about keeping your machines in good condition. For more details, don't hesitate to contact a member of our team who will be happy to assist you with any concerns.