4.320 MLS Head Gasket .045 - BBC

The 4.320 MLS Head Gasket .045 from COMETIC GASKETS is engineered for serious BBC (Big Block Chevy) engine builders and enthusiasts who demand reliable sealing under extreme compression and temperature swings. This gasket exists because stock gaskets fail under high-boost conditions, nitrous oxide injection, or sustained high-RPM operation—situations where combustion pressures exceed 200+ PSI. Whether you're building a street machine, a bracket racer, or a marine powerhouse, a quality multi-layer steel gasket is non-negotiable for cylinder head integrity.

The .045-inch thickness designation indicates the compressed gasket height, a critical parameter that directly affects the combustion chamber volume and static compression ratio. Cometic's MLS (Multi-Layer Steel) construction uses three or more stainless steel layers with elastomer coating, eliminating the soft asbestos or graphite facings that deteriorate under thermal cycling. The 4.320-inch bore diameter is purpose-built for BBC blocks and pairs perfectly with OEM or modern CNC-ported cylinder heads. This gasket's spring-back characteristics and dimensional stability make it ideal for both naturally aspirated and forced-induction applications, maintaining a reliable seal across wide operating windows without requiring constant retorquing.

Serious engine builders—particularly those running 427, 454, or stroker BBC combinations—rely on MLS gaskets because they withstand repeated heat cycles and high-pressure transients that destroy conventional gaskets. Installation requires proper head bolt torque sequencing and a clean, flat deck surface; deviations here negate even the best gasket. This gasket is compatible with standard BBC cylinder heads and late-model LS-based BBC conversions, making it a versatile choice for vintage restorations, performance rebuilds, and full engine swaps. Verify your specific bore diameter and application before purchase to ensure optimal compression ratio targets.