4.630 MLS Head Gasket .120 - BBC

The 4.630 MLS Head Gasket .120 - BBC from COMETIC GASKETS is engineered for serious Big Block Chevy engine builders and performance enthusiasts pursuing maximum reliability in high-compression, high-boost applications. Multi-layer steel (MLS) construction has become the industry standard for high-performance engines because it seals consistently under extreme cylinder pressures and thermal cycling that would compromise traditional composite gaskets. Whether you're assembling a street engine, bracket racing platform, or stroker combination, this gasket delivers the proven sealing integrity that separates a bulletproof build from a catastrophic failure.

The .120-inch thickness is precisely engineered to work with your specific BBC deck height and combustion chamber volume; deviating from the correct gasket thickness alters compression ratio and can cause quench or piston-to-head clearance issues. The 4.630-inch bore diameter matches standard BBC applications, while the multi-layer steel construction sandwiches spring steel and elastomer layers to maintain a gas-tight seal across repeated heat cycles—critical when engine temperatures spike into the 220–240°F range during sustained boost or high RPM operation. Cometic's MLS technology resists blowby and coolant seepage far better than older composite designs, especially in turbocharged or supercharged builds where cylinder pressures exceed 400 PSI.

This gasket is the right choice for any BBC platform demanding professional-grade sealing: street 427s, big-inch strokers, blown fuel systems, and naturally aspirated race motors all benefit from MLS reliability. Proper head bolt torque sequencing and fastener quality are mandatory—use ARP studs or quality OEM bolts torqued to specification to ensure gasket compression and long-term seal integrity. Installation requires clean, flat deck and cylinder head surfaces; use a torque wrench and follow your engine builder's specifications religiously to avoid leaks that cost time and money on the dyno or at the track.