Cummins ISX and N14 Engines: Tips and Tricks for Rebuild

The N14 and ISX engines are some of the most popular engines Cummins has produced, and even though the N14 has been out of production for years, many are still in use today. If you're one of those people who is running either the N14 or the ISX, odds are you'll need to do a rebuild at some point. We've compiled some tips and tricks to help you make the most of your next rebuild on your N14 or ISX.

Tips for the N14

Cummins N14 Engine | Highway & Heavy Parts

Completing an inframe rebuild on an N14 is fairly standard, but you shouldn't ignore the camshaft when you do it. The rebuild gives you the perfect opportunity to investigate for any additional signs of wear.

When you begin the rebuild, you'll drain the coolant and oil and remove the oil pan from the engine. If you're proactive (which can help save you time and money later on. And hey, what does it hurt to take a look?) as soon as the oil pan is removed, check the camshaft for any signs of additional wear.

If you don't, and you decide to just go ahead and complete the rebuild, you might shortly develop a miss in your engine. This miss might be caused by a camshaft failure. If there is extensive wear on the camshaft, you could experience a more major failure.

An inframe rebuild doesn't automatically include the camshaft. Instead, it's two separate repairs that don't always get done at the same time. Completing them together is a proactive step that can save you some downtime later on.


Tips for ISX

Cummins ISX Engine | Highway & Heavy Parts

Problematic Vibrations

Unlike on the N14, removing the camshaft is more a part of the rebuild process on the ISX. Once the camshaft or camshafts have been removed it's a good idea to check for other signs of wear.

On some ISX applications, the sumps are located behind the axle. On these rear sump applications, there's a long suction tube (2 ½ feet) that sucks oil from the oil pan. As the engine operates, this tube has a tendency to vibrate, which sets up a harmonic. The oil pan is made of aluminum, and this harmonic can cause the o-ring to wear the aluminum. This creates a spot for the air to get through to where the lubricating oil should be. Air is not a good lubricant, and its presence can negatively affect the application of your engine brake.


Whenever you're working on your engine, cleanliness is very important. This is especially true of an ISX. This engine is highly sensitive to debris, and it especially becomes an issue when the oil passages are exposed. If debris gets in those passages it can damage other components, like the crankshaft.

These passages should be protected immediately after exposure. There are four openings on the top deck of the cylinder block: two front and two rear. Make sure that plugs are properly placed to prevent further damage to your engine.

General checks

It's also a good idea to take a minute or two to observe everything. For instance, check the rocker arm to see if the bushings show signs of wear. If copper is showing, then it's a good indication that you should replace them.

Don't just tear it apart and set the components aside. You want to make sure everything that goes back in is serviceable. This will save you time and headaches later. Most of this can be done visually, and you'll end up thanking yourself for the extra effort you put in.


Pre-2250 Engines (with the injector cam)

If you run your pre-2250 engine for 5-10 minutes after assembly, it could be helpful to do a second injector setting. When running, the engine could adjust itself to its normal travel pattern, which could be out of alignment.

This is only a suggestion, but could minimize comebacks. This situation is more true on the N14 because of the amount of valve train components, leading to an increase in the stackup.


A little bit of extra maintenance can help keep your Cummins engine running at its best. Let our techs help you find the right parts for your rebuild! Call them at 844-304-7688, or you can request a quote online.

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