Cummins NT855 Engine Parts - Piston Kit Section

Cummins NT855 Engine Piston Kits: Complete Catalog

The Cummins NT855 engine is one of the most recognized heavy-duty diesel powerplants in the industrial and marine sectors. Known for its rugged design, long service life, and broad CPL (Control Parts List) compatibility, this engine has powered everything from off-highway machinery to standby generators and workboats. One of the most vital components in preserving its performance over time is the piston kit—ensuring optimal combustion, compression, and overall engine balance.

At Diesel Pro Power, we provide professionally matched piston kits and related components designed to fit a wide range of NT855 CPL numbers. Whether you're rebuilding a legacy NT855 engine or replacing worn internals in a high-mileage NH855, our comprehensive catalog is engineered to meet OEM specifications with maximum reliability.

Understanding NT855 Compression Ratios and Their Impact

When selecting the correct piston kit for your Cummins NT855 or NH855 engine, understanding the compression ratio is critical. Compression ratio refers to the volume difference in the cylinder between the bottom and top of the piston stroke. A higher ratio generally means better thermal efficiency and more power, but it can also increase stress on internal components. Here's a breakdown of the compression ratios available in our piston kit offerings:

14.0:1 Compression Ratio

Ideal for many mid-range NT855 configurations, the 14.0:1 ratio provides a balance between power output and mechanical durability. This compression profile is commonly found in CPL numbers such as 449, 481, 482, 500, 510, 531, 554, and many more.

14.5:1 Compression Ratio

Used in a wider range of CPLs, including many of the earliest NT855 engine configurations (CPLs 1 through 20+ and beyond), this ratio slightly increases combustion pressure, which is helpful in applications requiring more torque under load. With compatibility across over 150 CPL numbers, it's a versatile piston kit for multiple rebuild scenarios.

17.0:1 Compression Ratio

High-compression pistons like the 17.0:1 are typically used in applications where fuel efficiency and combustion completeness are key—such as in fixed-site power generation or high-altitude operating environments. Supported CPLs include 838, 840, 1187, and 1352.

Complete Piston Kits for Cummins NH855 and NT855 Engines

Each NT855 piston kit offered by Diesel Pro Power includes the following key components:

• One-piece piston (aluminum alloy construction)

• Piston pin (hardened steel, press-fit compatible)

• Retaining rings (when applicable)

• Oil ring groove support

• Optional skirt coating for anti-friction protection

These kits are machined to match exact tolerances required for Cummins engines and are available for standard and custom CPL configurations.

Piston Kit – 14.0:1 Compression Ratio

Applications: Suitable for CPLs such as 449, 481, 500, 510, 554, 575, 625, 695, 745, 808, 1167, 1179, 1411, and many others.

Design Notes:

• Recommended for industrial NT855s operating in medium-duty cycles.

• Compatible with standard fueling maps.

• Strong top ring land to resist heat distortion.

• Oil control features include reinforced ring grooves.

Piston Kit – 14.5:1 Compression Ratio

Applications: Designed to fit a large number of early CPLs, ranging from CPL 1 through 1409. This piston design is one of the most widely used across NT855 rebuilds.

Design Notes:

• Balanced for general-purpose engines.

• Enhanced fuel efficiency and smooth combustion.

• Designed to work with older-style combustion bowls and connecting rods.

• Offers a balance of performance and longevity, making it suitable for both power generation and mobile equipment.

Piston Kit – 17.0:1 Compression Ratio

Applications: Targeted at CPLs 838, 840, 1187, and 1352. These high-compression pistons are engineered for applications demanding peak combustion performance.

Design Notes:

• Ideal for turbocharged engines in high-load environments.

• Increases cylinder pressure for better thermal efficiency.

• Used in stationary generator sets and demanding marine applications.

Cylinder Liners for Cummins 855 Engines

A full piston rebuild isn’t complete without precision-fit cylinder liners. Diesel Pro Power offers multiple liner styles to meet various build years and fitment needs.

Standard Cylinder Liner (Dry Press Fit)

• Application: NH855, NT855, and N14 engines

• Fitment: Standard liner used in most rebuilds where wear has not exceeded tolerance

• Material: Hardened cast iron with honed inner surface

• Compatibility: Matches all NT855 piston kit variants

Oversized Cylinder Liners (0.020"/0.040")

For rebuilds where the cylinder block bore has worn or been machined oversize, Diesel Pro offers liners in both 0.020" and 0.040" press-fit dimensions.

• Material: Cast iron with low-friction coatings

• Press Fit: Lower press fit models available to accommodate older block configurations

• Surface: Fully honed and ready for installation

Piston Ring Sets for Cummins NT855 Engines

Proper sealing is essential to combustion and oil control. We provide two major ring set types:

Standard Ring Set

• Usage: Designed for routine overhauls and general-purpose applications

• Material: Hardened steel with moly-coated compression rings

• Includes: Compression rings, oil scraper, and expander ring

• Compatibility: One set per piston; matches all 14.0:1 and 14.5:1 piston kits

Premium Ring Set

• Usage: For high-load or high-mileage applications

• Material: Upgraded steel with enhanced heat resistance

• Coating: Chromium or ceramic-moly blend for increased lifespan

• Benefits: Improved wear resistance, oil control, and compression seal

• Ideal for: Industrial and marine rebuilds where uptime is critical

Cylinder Liner Seals & O-Rings

Each liner requires proper sealing components to prevent coolant intrusion and maintain block pressure integrity.

Liner Seal Ring

• Shape: Round or rectangular depending on liner design

• Function: Ensures tight seal at the base of the liner

• Use: One required per liner

• Material: Nitrile or high-heat-resistant polymer

O-Ring Seal

• Function: Dual-ring system provides redundant sealing at the liner flange

• Use: Two per liner

• Material: High-resilience synthetic rubber

• Compatibility: Designed for NT855 and N14 cylinder blocks

What’s Included in a Full Piston Kit Order?

When you order a complete piston kit from Diesel Pro Power, you receive:

• Pre-assembled piston with pin

• Optional rings (standard or premium, depending on selection)

• Retaining clips or locks (if required)

• Clear CPL compatibility guidance

• Optional liner and seal bundle

This helps eliminate guesswork and ensures your NT855 rebuild stays on schedule and within spec.

Why Choose Diesel Pro Power for NT855 Rebuild Kits?

With over 40,000 satisfied customers worldwide, Diesel Pro Power has earned a reputation for high-quality engine parts, fast shipping, and reliable support. Here’s why our piston kits for Cummins 855 engines are trusted globally:

• OEM Fitment Guarantee: Every kit is verified for CPL accuracy.

• Industry Expertise: We specialize in heavy-duty diesel platforms.

• Global Logistics: Fast shipping to North America, South America, Asia, and beyond.

• In-Stock Reliability: No long lead times. We keep NT855 kits ready to ship.

How to Identify the Correct CPL for Your NT855

Your engine’s CPL (Control Parts List) is the key to ordering the correct piston kit. It can be found stamped on the dataplate attached to your engine block. Always match your rebuild parts based on this number—not just the engine family (NT855 or NH855).

• CPLs with 14.0:1 Pistons: 449, 481, 575, 625, etc.

• CPLs with 14.5:1 Pistons: Hundreds available—especially CPLs 1 through 150+

• CPLs with 17.0:1 Pistons: 838, 840, 1187, 1352

If you’re unsure of your CPL, contact our parts support team for fast assistance.

Additional Notes for Installers

• Torque Specs: Always follow Cummins factory specifications when torquing piston pins, rod bolts, and head studs.

• Liner Installation: Check press fit clearance and install with recommended sleeve compound.

• Ring Orientation: Install ring gaps in correct offset positions to ensure sealing.

• Lubrication: Use clean engine oil or assembly lube during piston and liner installation.