It’s out of a 2001 Dodge Ram 2500, 5.9L 24V Cummins.

I bought the truck as a project with plans to completely rebuild the engine and transmission, eventually making it a higher-horsepower street truck.

While tearing down the engine, I discovered this damage to piston #2. I’m trying to figure out what caused it so I can address the issue before rebuilding everything.

Damage - A chunk of material is missing from the outer edge of the piston crown, near the cylinder wall.

Could this have been caused by a faulty injector, excessive cylinder temperatures, improper tuning, or something else?

I don’t know the truck’s previous tuning or maintenance history, and I haven’t had the injectors tested yet.

Any advice on what could have caused this or what else I should inspect would be appreciated.

Engine information and history

• Cummins 5.9L 24-valve industrial diesel
• Engine serial number (ESN): 45528729
• CPL: 2080
• Originally equipped with a VP44 injection system
• Converted to a Bosch P7100 injection pump
• Original pistons identified by Cummins as Grade C, part number 3800325

I purchased this engine as a Cummins ReCon with approximately 75,000 miles on it. It was previously installed in a Freightliner RV.

I don't know how the engine was operated or maintained during those 75,000 miles.

After installing it in my truck and converting the injection system, I put approximately 3,500–3,700 miles on it. The engine ran extremely well and made excellent power before developing progressively worsening blue smoke, excessive blow-by, oil consumption, and difficult cold starting.

What I found during teardown

After removing the cylinder head, I discovered that No. 5 piston had a substantial portion of its upper ring land broken away, with damaged rings and localized pitting around the edge of the crown.

I removed No. 6 piston for comparison. It appears considerably healthier, although there is some minor pitting on its crown.

The No. 5 piston skirt and connecting-rod bearing appeared to be in good condition.

Cylinder condition

There is no significant ridge at the top of the cylinders. I can feel a very slight transition where the rings stop traveling, but nothing substantial.

There is no scoring on the cylinder walls. No deep scratches, gouges, or damage that catches a fingernail.

There are some dark vertical marks and staining visible in the cylinders, but the surfaces remain smooth.

I lightly honed No. 5 for approximately 20–30 seconds using a three-stone spring-loaded hone. The crosshatch is visible across the previously dark areas, and the cylinder remains smooth.

I'm not attempting to remove every discoloration or hone away significant material.

Cylinder bore measurements

These measurements were taken using a telescoping bore gauge and digital caliper. I recognize that this equipment has limitations compared with a dial bore gauge, particularly when measuring differences of a few ten-thousandths.

The important observation is that the other cylinders are relatively consistent, while No. 5 measures approximately 0.003" larger in the direction corresponding to the piston damage.

Despite that difference, the cylinder wall remains smooth, with no substantial scoring or pronounced ridge.

Fuel injection system

The engine was originally equipped with a VP44 injection system and was converted to a Bosch P7100.

A local diesel fuel-injection specialist who is an authorized Bosch dealer and rebuilds and tests diesel injectors supplied the injectors specifically for this conversion.

The shop was provided with the engine information and an original injector when selecting the replacements.

These are eight-hole Bosch injectors, with the hole count confirmed by the specialist.

Injector markings:

• 176100139
• 043219363
• 4183
• Hand-engraved: C258369

After discovering the damaged piston, I brought the No. 5 injector back to the specialist for testing.

The injector passed testing, with no problems reported.

However, I have not independently established whether the injector's spray angle and pattern are compatible with the combustion bowl of the original Cummins 3800325 Grade C piston.

I'm particularly interested in determining whether the piston damage could be related to injector spray targeting, abnormal combustion, or something that occurred during the engine's previous service life.

My rebuilding plans

My preference is to replace all six pistons and rings, rather than repair only No. 5.

The minor pitting on No. 6 concerns me, particularly because I don't know what happened during the engine's previous 75,000 miles.

I'm trying to retain the original block, crankshaft, and connecting rods if they're serviceable.

I would prefer to avoid boring the cylinders or committing to a complete machine-shop rebuild unless measurements demonstrate that it's necessary.

I'm looking for a complete overhaul kit containing six pistons, rings, bearings, gaskets, and seals, preferably from a reputable aftermarket manufacturer.

Questions

1. Given the approximately 0.003" localized increase in bore diameter on No. 5, is there any reasonable possibility of reusing that cylinder with a standard-size piston and rings, or does it require machining?
2. Does anyone have the actual piston-to-wall clearance specifications for Cummins 3800325 Grade C pistons, including the proper piston measuring location?
3. Does anyone recognize these eight-hole Bosch injectors or know how to determine their spray angle and compatibility with the original Cummins combustion bowl?
4. Has anyone encountered similar upper ring-land failures or crown-edge pitting on a 5.9L Cummins? I'm particularly interested in possible causes beyond a defective injector, since the injector tested good.
5. Can anyone recommend a reputable aftermarket supplier offering a complete six-cylinder overhaul kit that maintains the correct Grade C piston geometry, combustion bowl, and wrist-pin specifications?

I'm not building a racing engine or looking for maximum horsepower. This is a working medium duty International truck, and my priority is long-term reliability.

I have the engine disassembled and accessible, but I would prefer not to send the entire block to a machine shop unless it's absolutely necessary. Nothing is guaranteed, but If my chances are decent I would go for the piston replacement.

I'm looking for practical advice based on actual engine-building experience and manufacturer specifications, particularly from people familiar with Cummins industrial engines and VP44-to-P7100 conversions.

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