4.350 MLS Head Gasket .040 - BBM

The Cometic Gaskets 4.350 MLS Head Gasket .040 is a multi-layer steel cylinder head gasket engineered for Mopar B and RB-series engines. With a 4.350-inch bore diameter and 0.040-inch compression thickness, this gasket delivers the precise sealing performance required for high-compression builds, street performance applications, and stock restorations alike. As an OEM-style replacement or performance upgrade, this gasket ensures consistent cylinder-to-head sealing across the entire engine block.

Cometic's multi-layer steel construction provides superior durability and reusability compared to single-layer gaskets. The MLS (multi-layer steel) design distributes clamping force more evenly across the sealing surface, reducing hot-spot stress and minimizing the risk of gasket failure under sustained boost or high combustion pressures. The 0.040-inch thickness specification is critical for maintaining proper compression ratio and valve timing clearance on B and RB-series platforms—choosing the correct thickness ensures accurate engine geometry without requiring additional machine work or shim stacks.

This gasket suits engine builders, restoration shops, and performance enthusiasts working with Mopar B-block and big-block RB-series engines. Whether assembling a numbers-matching factory rebuild, upgrading a street performance engine, or preparing a race platform, the correct head gasket specification is non-negotiable. The 4.350-inch bore matches late-model 340, 360, 400, 440, and related small and big-block Mopar variants, making this a versatile choice across the Mopar catalog. Precision fit and reliable sealing across thousands of heat cycles make this Cometic gasket a standard choice among Mopar builders.