The primary benefit of diesel engines over gasoline is their longevity. The massive torque and common industrial applications of diesel engines necessitate far sturdier components than other engines, which means that it takes a lot longer for them to wear out. If your diesel engine is in need of a rebuild, then you can rest assured knowing that (in all likelihood) this will be the last time it ever will. All the more reason to do it right the first time.
Before purchasing a rebuild kit, you'll need to have a clear goal in mind. If all you're planning to do is to re-fresh an old motor and get it back to the factory condition, then any rebuild kit will work. Factory rebuild kits are available at any automotive retailer like AutoZone or Pep Boys.
Odds are that you you can more than double your factory horsepower levels without replacing any of the engine's internal components. However, there are a few places that require attention if you're increasing boost and power levels.
The kind of kit you'll need depends largely upon the condition of your engine. Basic kits come with all basic wear items found in the engine: Piston rings, main and rod bearings, cam bearings, freeze plugs, oil pump and all of the gaskets to put everything together.
Whether you're building for performance or not, consider replacing the engine's lifters and water pump. The parts needed to rebuild a turbo are not included in most kits, so you might want to just go ahead and replace it with a re-built unit. This is highly recommended, as turbos see a lot of wear and tear over the years, which can seriously impact performance.
The pistons, connecting rods and crankshafts in most diesel engines are about as bullet-proof as parts come, but the piston rings and bearings are a different matter. Turning up the boost on any diesel engine puts a great deal of stress on the rod and main bearings, so upgrading to purpose-built race units (like those available from ACL or King) is a good idea. Piston rings are another weak point for high-powered engines.
While you have the engine apart, it would be a good idea to treat your piston tops, cylinder head passages and exhaust manifold(s) with a ceramic thermal-barrier coating like those available from Swain or Xtreme Performance. These coatings are cheap, easy to apply and do a great job of keeping combustion heat inside the cylinder where it can do some good. Remember: heat is energy, and any heat that escapes the combustion chamber represents wasted fuel and potential. Ceramic coatings can increase power and fuel efficiency, while lowering engine and exhaust gas temperatures.
