Pair GM Chevrolet 5.0L 305 Mercruiser Cylinder Heads – Casting Numbers 059 and 520 | 12552520 12558059

Introducing the Pair GM Chevrolet 5.0L 305 Mercruiser Cylinder Heads – Casting Numbers #059 and #520, specifically designed to restore and optimize the performance of your 5.0L GM Chevrolet or Mercruiser marine engine. These high-quality cylinder heads are built to meet or exceed OEM specifications, ensuring a perfect fit and reliable performance in your marine applications.

Crafted with precision engineering, these heads feature the #059 and #520 casting numbers, making them the ideal replacement for worn or damaged components in your GM Chevrolet 5.0L engine. Whether you’re upgrading for improved reliability or conducting an engine rebuild, these cylinder heads offer the durability and performance necessary for demanding marine environments.

Built from high-strength materials, these heads are designed to withstand the extreme conditions that marine engines face, including high heat and constant exposure to moisture. Fully assembled with valves and springs, they allow for quick and easy installation, minimizing downtime and getting your boat back on the water faster.

Key Features:

• Compatible with GM Chevrolet 5.0L 305 and Mercruiser marine engines
• Casting numbers #059 and #520 for OEM fit and performance
• Fully loaded with valves and springs for hassle-free installation
• Designed for marine applications, offering excellent heat resistance and durability
• Ideal for engine rebuilds, repairs, or upgrades
• Core Return Required

Applications:

• Fits GM Chevrolet 5.0L 305 and Mercruiser marine engines

Whether you’re performing routine maintenance, engine rebuilds, or simply looking to restore your boat’s performance, these cylinder heads offer reliable power and long-lasting durability. Designed to handle the harsh conditions of marine environments, they ensure your engine performs at its best, no matter where your adventures take you.

Heavy Duty Parts Company – Core Returns Policy

At Heavy Duty Parts Company, core returns are essential to our ability to provide high-quality, cost-effective cylinder heads to our customers. These returned cores supply essential components, such as keepers, springs, and retainers, which are critical to engine performance.

No Core Charge – Just Send It Back!

Unlike other companies, we do not charge a core fee upfront. Instead, we rely on our customers to return their used cores to keep our supply chain running smoothly.

Why Core Returns Matter

• Many small but essential parts from cores are reused to maintain OEM-quality cylinder heads.
• Returning cores keeps prices competitive by reducing the need for costly new components.
• It supports sustainability by minimizing waste and conserving resources.

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!

Shop

Mercruiser