Cummins NT855 Engine Parts - Engine Overhaul Kit Section

Cummins NT855 Engine Overhaul Kits and Related Components

The Cummins NT855 engine is a legendary platform used in heavy-duty industrial, marine, and power generation applications around the world. As one of Cummins’ most durable and widely used large-bore diesel engines, it offers a unique combination of mechanical simplicity and long-term serviceability. Whether you're rebuilding an engine in a dredging vessel, oilfield rig, or industrial generator, Diesel Pro Power offers comprehensive overhaul kits and supporting components tailored to the NT855 platform.

With over 40,000 satisfied customers worldwide, Diesel Pro Power is a trusted source for Cummins parts and rebuild kits. We offer OEM-quality solutions for all CPL variants and compression ratios of the NT855.

Understanding the Cummins NT855 Engine

The NT855 is an inline six-cylinder diesel engine with a displacement of 855 cubic inches (14.0 liters). It belongs to the broader Cummins 855 family and is the turbocharged counterpart to the naturally aspirated NH855. The NT855 series includes various sub-models such as the NTA855 (turbocharged and aftercooled) and Big Cam versions, each known for their rugged reliability and widespread use in stationary and mobile applications.

Thanks to its wet-sleeve design, mechanical fuel system, and heavy-duty construction, the NT855 is highly rebuildable—making overhaul kits an economical solution for equipment owners and maintenance managers seeking to extend service life without replacing the entire engine.

Complete Engine Overhaul Kits for Cummins NT855

We offer several overhaul kit options to suit your NT855 rebuild based on CPL number and desired compression ratio. All kits come with premium-grade internal components engineered to meet or exceed Cummins specifications.

Overhaul Kit: 14.0:1 Compression Ratio

This kit is designed for engines requiring a 14.0:1 compression ratio and fits a broad range of CPLs, including:
449, 481, 482, 500, 510, 531, 554, 575, 588, 625, 657, 695, 745, 757, 808, 849, 880, 1167, 1171, 1179, 1180, 1181, 1183, 1194, 1197, and 1411.

Key Benefits of 14.0:1 Compression:

• Optimized balance of power and durability

• Ideal for marine engines and stationary gensets operating at moderate altitudes and temperatures

• Reduces stress on cylinder liners and valves during combustion

Kit includes:

• 6 pistons with rings (14.0:1 dome profile)

• Cylinder liners

• Piston pins and retainers

• Main and rod bearings

• Upper and lower gasket sets

• Thrust washers

Each component is carefully matched for compatibility with the CPL list specified to ensure a smooth rebuild process.

Overhaul Kit: 14.5:1 Compression Ratio

For high-torque applications or engines that operate in colder climates, this 14.5:1 compression kit provides slightly improved cylinder pressures, combustion efficiency, and cold-start characteristics.

Compatible with a large number of CPLs, including 1 through 13, and many others up to CPL 1416.

Key Features:

• Greater thermal efficiency and torque at low RPM

• Common in early-generation NT855 and marine auxiliary engines

• Suitable for applications needing quick throttle response or long periods of low-speed operation

Kit Contents:

• Pistons and liners configured for 14.5:1 compression

• Full bearing set (available in standard and oversize)

• Cylinder head and lower gasket sets

• Piston pins and hardware

This kit is one of the most frequently ordered rebuild kits due to its broad CPL coverage and reliable performance characteristics.

Overhaul Kit: 17.0:1 Compression Ratio

Engines with CPLs 838, 840, 1187, and 1352 typically use this high-compression configuration. The 17.0:1 kit is ideal for NT855 applications operating at high altitudes or in fuel-limited regions, where maximizing combustion efficiency is critical.

Advantages:

• Increased fuel efficiency

• Better burn characteristics

• Higher power density for turbocharged applications

Important Note: With a high compression ratio like 17.0:1, engine builders must ensure proper calibration of the fuel injection system and cooling circuit. Overheating or excessive knock can occur if support systems are neglected.

Piston Cooling Nozzles

Piston cooling is essential during an overhaul, especially for NT855 engines under constant load. These nozzles spray oil directly under the piston crown to keep combustion temperatures under control.

Product Details:

• Requires six nozzles per engine

• Includes O-ring seals

• Reduces piston thermal distortion

• Helps extend piston ring and liner life

Installing new cooling nozzles during your overhaul is strongly recommended to avoid hotspots and premature wear.

Valve Calibration Tool: Feeler Gauge Set

After a full engine rebuild, proper valve lash is critical. Diesel Pro Power offers a professional-grade feeler gauge set (.002" to .025") designed for Cummins and Detroit Diesel platforms.

Used For:

• Valve adjustment during reassembly

• Routine valve lash inspection post-break-in

• Accurate valve clearance tuning for compression recovery

Using a precise feeler gauge ensures your rebuilt engine breathes correctly and avoids unnecessary valve or rocker arm wear.

Fuel Filters and Water Separators

Protect your investment after a rebuild with fresh fuel filtration. Diesel Pro Power offers OEM-style fuel filters and water separators compatible with the NT855 fuel system.

Fuel Filter – Standard

• Diameter: 2.813"

• Height: 4.57"

• Thread: M16 x 1.5" - 6

Fuel Filter + Water Separator – Medium

• Diameter: 3.02"

• Height: 5.62"

• Thread: M16 x 1.5" - 6H INT

Fuel Filter + Water Separator – Large

• Diameter: 4.65"

• Height: 10.24"

• Thread: 1/4" - 12 UN

Using fresh fuel filters post-overhaul prevents injector clogging and supports proper break-in.

Installation Tools

Having the right tools on hand is essential for a clean and damage-free rebuild. Diesel Pro Power offers:

Piston Ring Assembly Tool

• Helps compress rings during piston installation

• Reduces risk of ring breakage or liner scoring

• Compatible with Cummins and Detroit Diesel

Fuel Filter Removal Wrench

• Adjustable 3-7/16" to 3-3/4"

• Makes filter changes quick and safe

• Prevents overtightening or housing damage

Oil Filter Removal Wrench

• Adjustable 4-21/32" to 5-5/32"

• Heavy-duty design for tight access

Thermostats for NT855 and Big Cam Variants

Two thermostat options are available based on engine type:

• Standard Thermostat – 180°F

• Fits most NT855 and NH855 applications

• Supports optimal operating temp range

• Big Cam Thermostat – 185°F

• Designed for Big Cam variants of the NT855

• Slightly hotter operating temp improves emissions and warm-up time

Replacing the thermostat during overhaul helps prevent overheating and ensures the rebuilt engine reaches ideal temperature quickly.

Radiator Cleaner

A clean cooling system is vital to protect your new pistons, liners, and cylinder head. Diesel Pro Power's radiator cleaner dissolves internal scale and rust.

Key Uses:

• Flush coolant channels during overhaul

• Remove sediment that restricts flow

• Extend water pump and thermostat life

Recommended for both marine and land-based installations, especially if old coolant was contaminated or gelled.

Temperature Switch

Our temperature switch is compatible with Cummins NT855 engines and triggers at 205°F. Perfect for marine and industrial applications with monitoring systems, this switch can connect to alarms or automated shut-off devices.

Specs:

• Closes at 205°F

• Thread size: 1/2" NPT

Mechanical and Electric Gauges

Post-rebuild, it's essential to monitor the health of your NT855 engine. Diesel Pro Power offers a full suite of mechanical and electric gauges:

• Standard Mechanical Gauges: No power needed; reliable and durable

• Mechanical Gauges with Alarm: Adds visual/audible warnings

• 12V Electrical Gauges: Ideal for battery-based systems

• 24V Electrical Gauges: Common in marine, generator, and heavy-equipment panels

Use these gauges to track:

• Oil pressure

• Coolant temperature

• Fuel level

• Charging voltage

• Boost pressure

Installing gauges during your rebuild reduces downtime and protects your engine investment.

Why Choose Diesel Pro Power?

Whether you're managing a fleet of NT855-powered vessels or servicing a single industrial engine, Diesel Pro Power delivers trusted results with:

• Fast worldwide shipping

• Expert support to match kits to CPLs

• Thousands of in-stock Cummins parts

• No-hassle ordering from our online catalog

• Proven reliability with over 40,000 customers served

Every kit is backed by our dedication to quality, compatibility, and performance.