3943627 | Cummins ISB 5.9L 24 Valve Fully Loaded Cylinder Head, New | 5361587

3943627 | Cummins ISB 24V 5.9L Loaded Complete Reinforced New Cylinder Head | 5361587

Technical Specifications:

Fits: Cummins ISB 24V 5.9L engines

Displacement: 5.9L

Year range:  1998-2003

Cylinders: 6

Core Return Required

OEM Replacement # 3942628, 3943627, 3943628, 3943892, 3944991, 3944992, 3944993, 3944994, 3944995, 3945524, 3946202, 3937729, 3957403, 3990135, 3991771, 3991772, 3991773, 5361587

Product Information:

Introducing Heavy Duty Parts Companies reinforced, redesigned, and reinvigorated brand new cylinder head for the work horse of the industries the Cummins ISB. Our cylinder head has been redesigned to address the common flaws of the ISB head such as cylinder head cracking and pre-mature valve train failure. Our cylinder head is a heavy-duty aftermarket casting that is not only thicker internally in the crack prone areas of the head but also contains a higher nickel content in the cast iron casting. The cylinder head we offer comes fully assembled with valves, springs, retainers, valve locks, new high temp  viton valve stem seals and standard size cam bearings installed. Ready to install straight out of the box and bred to work. Out work the rest with Heavy Duty Parts best!

3943627 | Cummins ISB 24V 5.9L Loaded Complete Reinforced New Cylinder Head | 5361587

Product Overview

Enhance your Cummins ISB 24V 5.9L engine (1998-2003) with our high-performance Loaded Complete Reinforced New Cylinder Head. Designed to address and resolve common issues such as cylinder head cracking and valve train failures, this cylinder head is the ultimate solution for longevity and reliability.

Key Features

• Reinforced Design: This cylinder head is built with thicker internal casting in vulnerable areas and contains a higher nickel content, significantly reducing the risk of cracking.
• Premium Components: Fully assembled with high-quality valves, springs, retainers, valve locks, high-temperature Viton valve stem seals, and standard size cam bearings.
• Ready to Install: This cylinder head comes pre-assembled and ready for immediate installation, ensuring a hassle-free process and optimal performance right out of the box.

Technical Specifications

• Compatibility: Fits Cummins ISB 24V 5.9L engines (1998-2003), suitable for both electronic and non-electronic variations.
• Displacement: 5.9 liters.
• Cylinders: 6

Benefits

• Enhanced Durability: The reinforced design addresses common failure points, ensuring long-lasting performance.
• Improved Performance: Optimized airflow and combustion efficiency lead to better engine performance and fuel economy.
• Reduced Downtime: The pre-assembled nature of this cylinder head reduces installation time, getting your engine back to work quickly.

Purchase Information

Invest in the reliability and performance of your Cummins ISB engine with our top-quality cylinder head. For more details and to place your order, visit the product page.

Purchase and Shipping

We offer competitive pricing, and fast handling and shipping times. For more information on shipping times and costs, please visit our shipping policy page here.

Heavy Duty Parts Company – Core Returns Policy

Effective December 17, 2025

At Heavy Duty Parts Company, core returns are essential to our ability to provide high-quality, cost-effective cylinder heads. Returned cores supply critical components—such as keepers, springs, and retainers—that are vital to proper engine performance and allow us to maintain OEM-level quality.

No Upfront Core Charge

Unlike many suppliers, we do not charge a core fee upfront. Instead, we rely on customers to return their used cores within the required timeframe.

Core Return Requirements

• Cores are due within 30 days of the purchase date

• If a core is not returned within 60 days, the product warranty is void

• Unreturned cores will be charged as follows:

  • Cylinder heads under $600: $200 per unreturned core

  • Cylinder heads $600 and above: $400 per unreturned core

Customers needing additional time may contact us to request an extension. Approved extensions will prevent core charges from being applied.

Core Return Process

Cylinder heads are shipped with prepaid core return labels included in packets attached to the outside of each box. If labels are missing, customers should contact us for replacements prior to returning the core.

Core Eligibility

Some cylinder heads do not require a core return. In certain cases, core requirements may be waived at our discretion.

Why Core Returns Matter

• Reused core components help maintain OEM-quality standards

• Core returns allow us to keep pricing competitive

• Recycling cores supports sustainability by reducing waste and conserving resources

This policy applies to all purchases made on or after December 17, 2025.

Send Back All Components

To ensure the quality and integrity of our remanufacturing process, we ask that you return all components that were originally included with your new cylinder head. This includes items such as:

• Rocker arms
• Camshafts (if applicable)
• Any other hardware that came with your purchase

Easy & Free Core Return Process

• Each purchase includes a prepaid core return label in a plastic sleeve on the box.
• Simply pack your core with all included components, attach the label, and drop it off with the carrier—no extra cost to you.
• Returned cores undergo inspection and recycling, ensuring maximum efficiency.

Customer Partnership & Sustainability

By returning your core and its components, you help maintain a reliable supply chain, ensuring we can continue offering top-quality products at the best prices. This process not only benefits your wallet but also contributes to a greener and more efficient automotive industry.

We appreciate your support in keeping our business and the industry running smoothly!

Additional Info

Check out Cummins Official Website here.

3943627 | Cummins ISB 24V 5.9L Loaded Complete Reinforced New Cylinder Head | 5361587