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.

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.

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. 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 engine performance.