Cummins NT855 Engine Overhaul Kit

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, ZEB Power offers comprehensive overhaul kits and supporting components tailored to the NT855 platform.With over 4000 satisfied customers worldwide, ZEB 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.

Category Overview

Kit Type Selection: In-Frame vs. Complete vs. Top-End

NT855 overhaul kits cover three rebuild scopes:

Top-End Kit

Replaces cylinder head components: valves, guides, seals, head gasket set. Indicated when compression loss is isolated to the head with no liner or bearing wear confirmed by measurement.

In-Frame Kit

Engine remains in the chassis. Replaces pistons, rings, liners, connecting rod bearings, and gaskets. Applicable when wear is confined to the upper end and main bearing clearance remains within Cummins specification (≤ 0.006 in / 0.152 mm). If compression test shows low cylinder pressure but oil pressure holds at rated speed, an in-frame rebuild is typically sufficient.

Complete Overhaul Kit

The engine fully disassembled. Adds main bearings, thrust washers, and camshaft bearings to the in-frame scope. Required when main bearing clearance exceeds tolerance, crankshaft journal shows taper or out-of-round beyond 0.001 in (0.025 mm), or sustained low oil pressure is confirmed. Attempting an in-frame rebuild on a worn crankshaft will not restore oil pressure.

If main bearing clearance has not been measured, sustained low oil pressure at rated speed (below 30 psi) is the field indicator that a complete overhaul is required rather than in-frame.

Kit Configuration by Compression Ratio

The NT855 is produced in three compression ratio variants. Compression ratio determines piston dome profile, liner geometry, and ring land dimensions — these components are not interchangeable across ratios.

14.0:1 — One-piece pistons. Balanced power and durability. Suited for marine and stationary genset applications at moderate altitude and temperature.

14.5:1 — One-piece pistons. Higher cylinder pressure at low RPM. Common in early NT855 production and marine auxiliary engines; preferred where cold-start performance or extended low-speed operation is required.

17.0:1 — One-piece pistons. Piston-cooled or aftercooled engines only. Maximizes combustion efficiency at high altitude or in fuel-limited regions. Fuel injection calibration and cooling circuit integrity must be verified before installation.

Order by CPL number — do not rely on compression ratio alone. Use the compatibility matrix below to confirm.

Symptoms Indicating an Overhaul Is Required

· Excessive oil consumption (above 0.5% of fuel consumption) — worn or stuck piston rings allowing oil into the combustion chamber
· High crankcase blowby pressure — compression gases bypassing rings, detectable at the crankcase breather outlet
· Progressive power loss — declining cylinder compression, confirmed below 400 psi per cylinder
· White or blue exhaust smoke under load — oil burning or coolant entering combustion from a failed head gasket
· Sustained low oil pressure (below 30 psi at rated speed) — main or connecting rod bearing wear; indicates complete overhaul scope
· Coolant loss without visible external leak — head gasket or liner seal failure

Single symptoms may indicate a component-level repair rather than full overhaul. Compression test and oil analysis results should confirm the rebuild scope before kit selection.

Which Rebuild Scope Do You Need

Note: For most NT855 scheduled rebuilds, an in-frame kit is the standard choice. A complete overhaul kit is indicated when crankshaft inspection shows journal wear beyond service limits.

Recommended Overhaul Interval

· Power generation (prime / standby): 20,000–24,000 operating hours
· Marine continuous duty: 15,000–20,000 hours
· Mining / oilfield high-load: 12,000–15,000 hours

Interval should be confirmed by oil analysis and compression test results, not hours alone.

Compatibility Matrix

To select the correct overhaul kit for a NT855 engine, locate the CPL number on the engine nameplate and match it to the corresponding compression ratio below.

CPL number not listed above? Submit an inquiry with your engine nameplate photo for confirmation.

Kit Contents

Kit contents vary by rebuild scope. The table below lists components included in each configuration.

Recommended co-replacement (not included in kit):
Individual component OEM part numbers available on request. Submit inquiry with CPL number(engine nameplate) and rebuild scope.

Quality Tier

NT855 overhaul kits are available in three quality tiers. Selection depends on equipment requirements, budget, and downstream warranty obligations.

Considerations by tier:

· Genuine kits include Cummins-issued part traceability documentation, required for some insurance and warranty claim processes. Lead time depends on regional distributor stock.
· OEM-Equivalent kits are produced on the same tooling lines as genuine parts in many cases. The principal difference is packaging and documentation, not component specification. Suitable for the majority of commercial overhaul programs.
· Aftermarket quality varies significantly between suppliers. Critical dimensional tolerances — piston ring gap, bearing clearance, liner bore finish — should be verified against Cummins service manual specifications before installation.

Tier availability for specific CPL groups varies. Contact us with your CPL number and rebuild scope to confirm which tiers are in stock.

What We Supply

NT855 overhaul kits are available in both Genuine Cummins OEM and OEM-Equivalent tiers. Orders are fulfilled based on application requirement and buyer preference — specify your requirement at inquiry stage and we will confirm availability, lead time, and pricing for the applicable tier.

CPL Identification Guide

The CPL (Control Parts List) number is the definitive reference for NT855 parts ordering. It is stamped on the engine nameplate, located on the right side of the block near the fuel pump.

Steps to identify your CPL:

Locate the dataplate on the engine block

Record the CPL number (3 to 4 digits)

Cross-reference with the compatibility matrix above

Confirm the compression ratio matches your application records

If the dataplate is missing or illegible: provide the engine serial number when contacting ZEB Power. CPL history can be retrieved from Cummins QSOL records using the serial number alone.

CPL 1181 note: This CPL appears in both the 14.0:1 and 14.5:1 compatibility lists. Verify the compression ratio from engine documentation or by direct measurement before ordering.

Procurement & Logistics

Lead Time & Stock

· Genuine Cummins kits: subject to regional distributor availability; typical lead time 7–21 business days depending on CPL
· OEM-Equivalent kits: stocked for high-frequency CPL groups (14.5:1 variants); confirm availability at inquiry
· Special variant kits: lead time confirmed at order; typically 10–15 business days

Minimum Order

· Single kit orders accepted
· Volume pricing available for 3 units and above
· Fleet overhaul programs (10+ units) handled on a project basis — contact for dedicated lead time and pricing

Packaging

· Export wooden crate
· Individual components bagged and labeled
· Rust inhibitor applied to bare metal surfaces
· Gross weight approximately 104–115 kg per in-frame kit

Export Documentation

· Commercial invoice
· Packing list
· Certificate of Origin (on request)
· Any additional documentation required by destination customs confirmed at order

Shipping

· Sea freight (FCL / LCL): available to all major ports
· Air freight: available for urgent single-kit orders
· DDP / DAP terms available on request
· Transit damage: all shipments photographed pre-dispatch; damage claims supported with pre-shipment evidence

Warranty & After-Sales

Warranty Coverage by Tier

· Genuine Cummins kits: warranty terms follow Cummins standard policy; coverage period and conditions determined by regional Cummins distributor at point of sale
· OEM-Equivalent kits: 12 months from date of installation or 14 months from date of shipment, whichever occurs first; covers manufacturing defects in materials and workmanship
· Aftermarket kits: 6 months from date of shipment; dimensional conformance to Cummins service manual specifications is buyer's responsibility to verify prior to installation

Warranty Exclusions

· Damage resulting from incorrect kit selection (wrong CPL group)
· Installation without following Cummins NT855 service manual torque specifications and procedures
· Engine overspeed, fuel contamination, or lubrication system failure
· Components modified or machined after delivery

Claim Process

· Step 1: Document the issue — photograph failed components, record engine hours at failure and CPL number
· Step 2: Submit claim within warranty period — provide photos, CPL, ESN, and order reference
· Step 3: Assessment within 5 business days — replacement or credit issued upon confirmation of manufacturing defect

Technical Support

· CPL and kit selection confirmation prior to order
· Cummins service manual torque specifications and assembly sequence available on request
· Installation query support via email — response within 1 business day

FAQ

Q1: Can overhaul kit components be used across different compression ratios?

No. Piston dome profile, liner geometry, and ring dimensions differ between the 14.0:1, 14.5:1, and 17.0:1 kits. Mixing components across compression ratios will result in incorrect compression and potential engine damage.

Q2: My NT855 CPL number is not listed in the matrix — what should I do?

Submit your engine serial number via the inquiry form. ZEB Power can retrieve CPL history from Cummins records and confirm the correct kit specification.

Q3: CPL 1181 appears in two compression ratio lists — which kit should I order?

CPL 1181 is listed under both 14.0:1 and 14.5:1. Confirm the actual compression ratio from the original engine documentation or by direct measurement before placing an order.

Q4: Does the 17.0:1 kit require any additional components beyond what is included?

Yes. The 17.0:1 kit is designed for piston-cooled or aftercooled engines only. Fuel injection calibration and cooling circuit integrity must be verified prior to installation. Replacing piston cooling nozzles at the same time is strongly recommended.

Q5: Are NT855 and NH855 overhaul kits the same?

The NT855 (turbocharged) and NH855 (naturally aspirated) share the same block architecture. In-Frame and Top-End kits are common between the two for matching CPL numbers. Confirm CPL before ordering.

Q6: Are oversize bearing shell sets available?

Yes. Standard-size shell sets are included in all kits. Connecting rod and crankshaft shell sets in 0.010" and 0.020" oversize are available separately on request.

Q7: Can NT855 overhaul kit components be used in an NTA855 or Big Cam engine?

NTA855 (turbocharged and aftercooled) shares many components with the NT855 for matching CPL numbers. Big Cam variants use different cylinder head configurations and some internal geometry differences — confirm CPL compatibility before ordering. Do not assume interchangeability across variants without verification.

Inquiry

To receive pricing and availability for a NT855 overhaul kit, provide the following in your inquiry:

· Engine nameplate and CPL number
· Rebuild scope: Top-End / In-Frame / Complete
· Required quality tier: Genuine / OEM-Equivalent / Aftermarket
· Destination port and required documentation

Not Sure Which Kit You Need?

Send us your engine serial number and dataplate photo. We will identify the correct CPL, confirm the applicable kit variant, and provide a component-level breakdown before you commit to an order.

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