Dorman 674-425 Exhaust Manifold - Left

Dorman 674-425 Exhaust Manifold

Dorman 674-425 is a cast iron exhaust manifold engineered to match the fit and function of the original manifold on specified vehicles. It is built for the left side and includes the gaskets and downpipe hardware needed for a complete exhaust manifold repair.

• Cast iron construction for durability and heat resistance
• Round port shape with a 3-inch collector port diameter
• Oxygen sensor port included for direct sensor transfer
• Heat shield included to match OE-style thermal protection
• Standard replacement grade for factory-style fit and function
• Compatible with 2014-2018 Chevrolet Silverado 1500, left
• Compatible with 2014-2018 GMC Sierra 1500, left
• Compatible with 2017 Chevrolet Silverado 2500, left
• Compatible with 2018-2020 Chevrolet Express 2500, left
• Compatible with 2018-2020 Chevrolet Express 3500, left
• Compatible with 2018-2020 GMC Savana 2500, left
• Compatible with 2018-2020 GMC Savana 3500, left

Detailed Product Overview

This exhaust manifold is designed for vehicles that need a direct-fit replacement on the left side of the engine. The cast iron body helps manage exhaust heat, while the OE-style port layout, oxygen sensor provision, and included gasket set support a proper repair on Chevrolet Silverado 1500, GMC Sierra 1500, Chevrolet Express, and GMC Savana applications. Part number 674-425 is a practical choice when replacing a cracked, warped, or leaking manifold on the listed vehicles.

This part cross-references GM OE 12631812 for the same application.

Common Repair Symptoms

• Exhaust leak noise from the manifold area
• Visible cracking or warping in the original manifold
• Burning smell from escaping exhaust gases
• Check engine light related to exhaust or oxygen sensor readings
• Loss of exhaust sealing at the cylinder head or downpipe connection

Installation Notes and Tips

Verify left-side fitment before ordering and compare the original manifold, port layout, and oxygen sensor location to the vehicle. Inspect the cylinder head and downpipe sealing surfaces for damage before installation. Replace any worn fasteners or damaged sensors as needed during the repair, and follow the vehicle manufacturer’s torque sequence and specifications.

Quality Assurance

Dorman designs this manifold as a standard replacement part to match original fit and function on the specified applications. Part number 674-425 is manufactured for direct replacement use on the listed Chevrolet and GMC vehicles.