Edelbrock part #2992 Victor 18 Degree Spider base is the bedding plate portion of a two-piece (valley plate and spider) manifold system. This Spider base is intended for use with "Conventional" 18-degree SBC heads on a standard deck engine block. This plate is more compatible when using our older 18-degree intakes such as 2955 and 2958 and will require less work for proper fit.