4.160 MLS Head Gasket .040 - Pontiac 389-455

The 4.160 MLS Head Gasket .040 for Pontiac 389-455 is a precision-engineered sealing component designed for serious engine builders and restoration specialists working with classic Pontiac big-block platforms. This multi-layer steel (MLS) gasket addresses the critical challenge of maintaining a consistent, reliable seal between the cylinder head and engine block—a task that becomes increasingly demanding in high-compression applications, forced induction setups, or engines that have been overbored or stroked. Whether you're rebuilding an original 389, 400, 421, 428, or 455 cubic-inch engine for street performance or vintage racing, a quality head gasket is non-negotiable for preventing coolant leaks, combustion gas escape, and long-term reliability.

Cometic Gaskets engineered this 4.160-inch bore diameter gasket with a .040-inch thickness MLS construction, which uses multiple stainless steel layers bonded to a composite facing material to provide superior conformability and clamping load retention compared to traditional cork or single-layer designs. The MLS technology excels at maintaining gasket compression under thermal cycling, resisting hot spot distortion, and delivering consistent sealing pressures across the combustion chamber and coolant passages. The .040 thickness specification makes this gasket compatible with stock or mildly modified cylinder head decks, ensuring proper fire ring positioning and combustion chamber volume matching—critical factors that directly impact compression ratio and detonation resistance in fuel-injected or carbureted applications.

This head gasket is ideal for anyone rebuilding a Pontiac 389-455 big-block engine who demands reliability and wants to avoid repeat teardowns due to head gasket failure. Installation requires proper deck surface preparation—clean, flat, and machined surfaces are essential for MLS gasket sealing—along with correct head bolt torque sequencing and specifications. Pair this gasket with quality head fasteners and follow your engine builder's recommended torque specs to ensure longevity. This is a core component for period-correct restorations, street performance engines, and vintage racing builds where proven sealing integrity is paramount.