4.125 MLS Head Gasket .040 Olds V8 330-455

The 4.125 MLS Head Gasket .040 Olds V8 330-455 from Cometic Gaskets is purpose-built for serious engine builders and mechanics restoring or modifying classic Oldsmobile V8 platforms. Whether you're rebuilding a stock 330, 400, 425, or 455 block, or pushing displacement with modern tuning, a properly specified head gasket is non-negotiable—it seals combustion pressure, prevents coolant and oil crossover, and ensures repeatable cylinder compression across the entire operating envelope. This multi-layer steel design handles both stock and boosted applications when paired with appropriate fastener torque and surface preparation.

Multi-layer steel (MLS) construction delivers superior conformability and reusability compared to older composite gaskets, critical for vintage iron blocks where deck surface flatness may vary within machining tolerances. The 4.125-inch bore diameter matches factory Oldsmobile cylinder dimensions, while the .040-inch compression thickness controls the gasket's contribution to final engine height and combustion chamber volume—a detail that affects both static compression ratio and detonation margin. Cometic's laser-cut precision ensures minimal bore overhang, reducing the risk of gasket extrusion under peak cylinder pressure and maintaining a consistent seal throughout thermal cycling.

This gasket serves street engines, race applications, and everything between; it is compatible with any machine shop capable of dial-indicating deck surfaces and proper torque sequencing. Installation requires meticulous deck cleaning (no residual carbon or old gasket material), use of correct head bolt torque specs for your block material (cast iron requires different fastener preload than modern aluminum), and follow-up retorque after the first heat cycle. Ideal for enthusiasts performing complete top-end rebuilds, cylinder head porting, or higher-compression builds where controlling chamber volume is essential for achieving target boost or ignition timing targets.