4.040 MLS Head Gasket .040 - SBM 5.2/5.9L

The 4.040 MLS Head Gasket .040 for Small Block Mopar 5.2/5.9L engines is a precision-engineered sealing solution designed for builders and enthusiasts who demand reliability in high-performance or stock-rebuild applications. Multi-layer steel (MLS) construction has become the industry standard for modern engine builds because it handles heat cycling, boost pressure, and combustion forces far better than traditional composite gaskets. Whether you're assembling a fresh short-block for a street engine, preparing a truck for increased boost, or restoring a classic Mopar to factory specifications, this gasket delivers the seal integrity that prevents coolant seepage, oil migration, and compression loss.

Cometic Gaskets manufactures this head gasket using proprietary MLS technology that employs multiple hardened steel layers bonded with elastomer compounds. The .040-inch compressed thickness is engineered to maintain a consistent clamping load across the entire sealing surface when torqued to specification, which is critical for preventing hot spots and uneven pressure distribution that can lead to localized failures. The 4.040-inch bore diameter matches the specifications of small-block Mopar heads, ensuring proper alignment with cylinder walls and combustion chamber geometry while the precision edge beading promotes rapid seating and reduces the risk of gasket movement during engine startup and thermal cycling.

This gasket is ideal for 5.2L and 5.9L small-block Mopar applications, including Dodge and Plymouth vehicles from the 1960s through early 2000s, as well as contemporary custom builds using vintage Mopar architecture. Proper installation requires cleaning both the block and cylinder head surfaces to bare metal, using a quality head gasket sealer (not sealant) on both sides, and torquing fasteners in the correct sequence to the engine manufacturer's specification—typically 65 to 75 foot-pounds for small-block applications. When combined with ARP fasteners and careful torque protocol, this Cometic gasket provides the foundation for an engine that will hold vacuum, maintain coolant integrity, and resist blowby even under sustained driving or boost conditions.