4.540 MLS Head Gasket .066 - BBC

The 4.540 MLS Head Gasket .066 - BBC from Cometic Gaskets is an essential sealing component for big-block Chevrolet engine builders and performance enthusiasts pursuing maximum reliability under high compression and boost. This multi-layer steel (MLS) gasket is engineered to maintain a consistent seal across the critical interface between the cylinder head and block, where combustion pressures, thermal cycling, and clamping load variations demand precision engineering. Whether you're rebuilding a street engine, preparing a competition platform, or restoring a classic muscle car, this gasket delivers the durability and conformity required to prevent coolant loss, oil weeping, and compression leaks that compromise both performance and longevity.

Cometic's MLS construction uses multiple embossed stainless steel layers bonded with advanced elastomers, allowing the gasket to conform to minor surface irregularities while resisting deformation under sustained pressure and temperature extremes. The .066-inch thickness is specifically calibrated for BBC (big-block Chevrolet) applications, matching OEM bore centers and valve cutout geometry to ensure proper port alignment and combustion chamber symmetry. This gasket excels in both naturally aspirated and forced-induction builds, maintaining its seal integrity even when head gasket pressures exceed 100 psi during peak boost or high-rpm operation. The 4.540-inch bore diameter accommodates the full spectrum of BBC configurations, from 427 to 502 cubic-inch stroker packages, making it a versatile choice for diverse engine platforms.

Serious engine builders and experienced technicians rely on this Cometic gasket for restorations, performance upgrades, and race engine assembly where standard gaskets fall short. Installation requires proper surface preparation—both block deck and cylinder head surfaces must be cleaned to bare metal and inspected for flatness—combined with correct head bolt torque sequencing and specifications unique to your block and head combination. The compact 9.75 x 0.25 x 24-inch footprint ships efficiently, and at just 1.5 pounds, handling is straightforward during the critical assembly phase. This gasket pairs seamlessly with quality head bolts, modern sealants, and precision-machined components to deliver the seal integrity that separates a long-lasting build from catastrophic failure.