Michigan Motorsports LS Engine Coolant Port Plug - 28mm Thread with 17mm Hex - Seals Unused Rear Coolant Passages - Replaces GM #12561663

When converting or modifying an LS engine setup, unused rear coolant ports often need to be securely sealed to prevent leaks and maintain optimal coolant flow. The Michigan Motorsports Coolant Port Plug is engineered specifically for LS engine blocks requiring a 28mm thread and 17mm hex head, serving as a direct replacement for GM part number 12561663. Whether you’re building a street setup or a high-performance track machine, this plug provides a precise, leak-free seal to complete your cooling system with confidence. Ideal for customers sealing off unneeded factory coolant passages during custom engine builds or swaps, this plug ensures a clean, professional-grade solution for LS cooling conversions.

• Seals Rear Coolant Passages: Designed to seal unused coolant ports on LS engine blocks, this plug is perfect for engine builds or conversions where specific cooling paths are no longer needed.
• 28mm Thread with 17mm Hex Head: Machined to match OEM specs, this plug features a 28mm thread and a 17mm hex head for simple installation using standard tools—no guesswork required.
• Direct Fit OEM Replacement: Replaces GM part number 12561663, making it a trusted choice for LS swaps, engine conversions, or performance builds requiring precise fitment and leak prevention.
• Ideal for Cooling System Customization: Whether adapting for rear coolant passage sealing or completing a custom engine configuration, this plug helps streamline your cooling layout cleanly and effectively.
• Trusted Michigan Motorsports Quality: Built to handle high-pressure cooling environments, this plug is made from high-quality materials and engineered to meet or exceed factory durability and performance standards.