Cummins QSB 4.5 Overhaul Kits & Rebuild Components

Engine Overview

The Cummins QSB 4.5 is a mid-range, 4-cylinder turbocharged diesel engine widely used in marine, industrial, agricultural, and construction applications. Known for its reliability, high power-to-weight ratio, and advanced electronic controls, the QSB 4.5 is built on the B-Series platform but incorporates Common Rail Fuel System technology and updated emissions components. Its compact footprint and responsive power delivery make it ideal for everything from excavators to generators and commercial vessels.

Proper maintenance and timely rebuilds are essential to extending the service life of this engine. If you're experiencing excessive oil consumption, hard starts, blue exhaust smoke, or decreased compression, it may be time to consider a full overhaul using a compatible rebuild kit.

Complete Rebuild Kits for Cummins QSB 4.5 by CPL Number

Diesel Pro Power offers complete in-frame overhaul kits for the Cummins QSB 4.5 that are matched by CPL (Control Parts List) number to ensure 100% compatibility. Each kit includes everything required for an in-frame rebuild: pistons, rings, liners, bearings, and gaskets.

Overhaul Kit for Cummins QSB 4.5 – CPL #1100, 1700, 1701, 2743, 8725, 8754, 8755, 8756

Piston Design: 1-piece piston
Fitment: Standard size components
Compression Ratio: Typically 17.2:1 or 17.3:1 depending on CPL. A higher compression ratio improves combustion efficiency but also increases internal stress, making it crucial to match the correct pistons.

This rebuild kit is ideal for engines with moderate wear that need restored compression and performance. Common failure symptoms for engines in this CPL range include:

• Difficulty starting when cold

• Loss of power under load

• Abnormal exhaust smoke during acceleration

• Blow-by or oil in the intake system

By replacing all major wearable components, this overhaul kit restores factory-level compression, seals, and piston clearance to bring your engine back to peak performance.

Supporting Components That Should Be Replaced During Rebuild

Piston Cooling Nozzles (Qty: 4)

Part Use: One nozzle per piston
Why it matters: These nozzles spray engine oil onto the underside of the pistons to reduce heat and prevent seizure during high-load operation. Replacing worn or clogged nozzles is critical during a rebuild to maintain piston cooling and avoid repeat damage.

Crankshaft Seal Kit – Front (Seal + Sleeve)

This front crankshaft seal kit ensures your engine remains oil-tight at the front timing cover. Ideal for engines that exhibit oil seepage or leaks near the accessory drive.

Crankshaft Seal Kit – Front (with Dust Shield)

Includes the crank seal and dust shield for engines that need improved protection in dusty or dirty operating conditions—common in construction or agricultural environments.

Crankshaft Seal Kit – Rear

For engines with a wet clutch housing, this double-lip rear crankshaft seal and sleeve kit ensures tight oil retention and helps prevent flywheel contamination.

Valve and Fuel System Servicing Tools

Feeler Gauge (.002" to .025")

Essential for setting valve lash to factory spec after replacing cylinder head components or gaskets. Proper lash settings ensure combustion efficiency and prevent valve seat damage.

Filtration Components to Replace During Overhaul

Fuel Filter

2.813" diameter | 4.57" height | Thread: M16 x 1.5
Recommended to replace during rebuild to prevent contaminants from damaging new injectors or fuel system components.

Fuel Filter with Water Separator

Removes water and particulate from diesel fuel. Especially important for marine or humid climates where fuel contamination is more likely.

Oil Filter

Spin-on style, 3.66" diameter, 5.35" height
Critical to swap during any rebuild to ensure clean oil feeds into new bearings, pistons, and liners. Using the old oil filter risks contaminating fresh engine internals.

Recommended Rebuild Tools

Piston Ring Assembly Tool

Ensures correct piston ring installation without damage. Prevents ring deformation and improper seating that could compromise cylinder compression.

Fuel Filter Removal Wrench (3-7/16" to 3-3/4")

Speeds up the fuel filter replacement process, especially in tight engine bays.

Oil Filter Removal Wrench (4-21/32" to 5-5/32")

For high-torque filter removal during disassembly or first service after break-in.

Optional But Recommended Service Add-ons

Radiator Cleaner

Helps flush sediment and scale from the cooling system. Especially recommended after engine rebuilds to ensure even cooling across cylinders.

Temperature Switch

Closes at 205°F and has a 1/2" NPT thread. Ideal if your engine experienced overheating issues prior to rebuild. Failure to address faulty switches can lead to repeat failures.

When Should You Rebuild a QSB 4.5?

While every application is different, these are common signs that indicate your Cummins QSB 4.5 engine may be due for an overhaul:

• Compression readings more than 15% below spec

• Frequent need to top off oil

• Hard starting, especially in cold weather

• Excessive blow-by from the valve cover

• Sudden drop in fuel efficiency

• High crankcase pressure readings

• Metal shavings found in oil filter

Why Buy Rebuild Kits from Diesel Pro Power?

With over 40,000+ satisfied customers worldwide, Diesel Pro Power specializes in providing engine-specific, CPL-matched rebuild kits for Cummins engines. Our kits are curated by diesel experts to include only top-quality components that meet or exceed OEM specifications. We also stock the tools and service parts you need to complete the job right the first time.