It's hard to believe no one has reviewed these guys yet. Very professional and detailed company it was a pleasure doing business with you. The answered the phone every time I called or answered every email in a timely manner! I will definitely use them for all my cylinder head needs moving forward. Thank again!
The experience was excellent. My part came sooner than expected and was exactly as advertised. This is how a business should be run. I would give 6 stars if I could, thank you HDPC
Product was as described and packaged well! Communication throughout prosses was also great! I will definitely be using them in the future with other projects.
Parts arrived as promised. Ported heads gave me that low end torque and high rev HP I was looking for! ...if only I did the cam at the same time.
GM Chevrolet 5.0L 305 Mercruiser New Cylinder Head – Casting Numbers 059 and 520 | 12552520 12558059 | No Core Required
$525.00
-
Additional Info
GM Chevrolet 5.0L 305 & Mercruiser Marine New Cylinder Head – Casting #059 / #520
Marine-Grade Precision Rebuild – Fully Loaded and Ready for the Water
Restore your engine’s mechanical integrity with this brand-new GM 5.0L (305) Marine cylinder head. Engineered for the high-duty cycles of Mercruiser and Volvo Penta applications, this fresh, high-density castings are free from the thermal fatigue and corrosion common in used Marine cores. Every unit is precision-finished in-house, including final guide sizing and multi-angle valve seat cutting on our Rottler equipment to ensure perfect geometry. To guarantee a high-pressure combustion seal, the deck is PCD-milled on our Rottler S85A to achieve the ultra-low Surface Roughness (Ra) required for long-term gasket retention in moisture-heavy environments. These heads are pressure-tested to 60 PSI and undergo ultrasonic cleaning of all internal cooling passages to ensure maximum thermal dissipation and out-of-the-box reliability
🛠️ In-House Machining Process
- Cleaning: Fully disassembled and thermally cleaned.
- Soda Blasted: Castings are blasted with Sodium Bicarbonate. Because baking soda is water-soluble, there is zero risk of abrasive media clogging oil passages.
- Pressure Testing: Tested to 60 PSI to ensure no cracks or porosity leaks.
- Surfacing: All heads are resurfaced on our Rottler S85A for a precision gasket-sealing surface.
- Valve Job: Multi-angle valve job performed; every port is Vacuum Tested to ensure valves are seated 100% airtight.
📊 Technical Specifications
- Engine Compatibility: GM Chevrolet 5.0L 305 / Mercruiser Marine
- Casting Numbers: #059 and #520
- Assembly: Fully loaded with valves and springs
- Marine Optimized: Enhanced heat resistance and durability for salt and freshwater use
🚛 Fitment Data
Common Applications:
- Mercruiser Marine: 5.0L 305 V8 Engines
- Chevrolet/GMC C/K 1500 & 2500: 1996–1999 (5.0L)
- Chevrolet Express / GMC Savana 1500 & 2500: 1996–2002 (5.0L)
- Application Note: Ideal for marine rebuilds and Vortec-era small block truck repairs.
[+] Click to View Full Detailed Fitment List
CHEVROLET 2500 PICKUP 96-98 8-305 (5.0L);
EXPRESS 1500 VAN 96-02 8-305 (5.0L);
EXPRESS 2500 VAN 96-02 8-305 (5.0L);
GMC 1500 PICKUP 96-99 8-305 (5.0L);
GMC 2500 PICKUP 96-98 8-305 (5.0L);
SAVANA 1500 VAN 96-02 8-305 (5.0L);
SAVANA 2500 VAN 96-02 8-305 (5.0L);
📦 Core Return & Warranty
- ❌ NO CORE REQUIRED — No core fee, no return needed. Your old part is yours to keep or dispose of as you see fit.
- Warranty: 2-Year Unlimited Mileage Warranty included. Click here for Warranty details.
Related products
-
New Loaded Duramax 6.6L GM Silverado Sierra Cylinder Head LLY | No Core Required
$700.00-
Add to cart -
New Pair Chevrolet GM Duramax 6.6 Diesel Cylinder Heads LB7 2001-2004.5 | No Core Required
$1,395.00-
Add to cart -
Brand New GM Ecotec Chevy GMC Buick 2.4L Direct Injection Cylinder Head # 279 Casting
$1,050.00-
Add to cart -
New Pair Mercruiser 7.4L 454 BBC Marine Cylinder Heads – Cast Iron Casting # 279 | No Core Required
$2,300.00-
Add to cart
Dedicated to Customer Satisfaction
What sets us apart from the competition is our dedication to customer satisfaction. We strive to make your shopping experience as seamless and convenient as possible. Our user-friendly online platform allows you to browse our comprehensive inventory, compare products, and place orders with ease. With secure payment options and swift shipping, you can trust that your order will arrive promptly, minimizing downtime and maximizing productivity.