Steel Loc-Wire O-Ring Head Gasket 1012 FE1012 Suit BB Chev, Suit Nitrous/Turbo Applications, 4.640" Bore, .039" Compressed Thickness, One Coolant Hole Per End BB CHEV 396 454 O-RING 4.640" Loc Wire head gaskets require precision receiver groove machined in cylinder heads.

Round bore; Will not fit some cylinder head valve pockets

Fits Mark IV Block

Pre-1971 blocks may require modifications

Fits Gen V Block

Fits Gen VI Block

One coolant holes per end.

Three lower coolant holes

Has large .510" dia. bolt holes

Designed specifically for nitrous and high boost applications,

Loc-Wire head gaskets use an oversized combustion sealing wire encased in a stainless steel armour to provide an extremely robust combustion seal.