When I replaced intake gaskets on my stock 1976 K20, 350, 4 bbl, the gasket set came with a selection of restrictor plates, the original restrictor plates were still intact, the instructions with the new gaskets had a chart for different applications depending on the duty type of truck, light duty called for no restrictors, medium duty use may call for a restrictor in one side only, heavy duty use would usually call for a restrictor in both sides, they were not intended to completely block the heat, they helped moderate the heat under the carburetor. Waveski is using an aluminum manifold, it will absorb and radiate heat much quicker than cast iron. FelPro, Victor, Mahle, and others will have those restrictor plates in specific gaskets sets. We know it is a balancing act to get a modified engine running correctly, especially if we don't know exactly what the internals are, in this case we don't know compression ratio and camshaft specs, we know the single plane manifold was not a good choice for street, the carb may not be perfect, etc. hopefully we can help Waveski get this thing in better shape.
