The 'gasket' should only come in contact with the 'mating' parts of an oberdorfer type pump HOUSING. If you totally 'cover' the 'side-plate' with any gasket material the impeller will 'tear' the gasket and may 'pull out' fibers from the 'mating surfaces'. Most oberdorfer vane pumps have the impeller vane coming in direct contact with the metal surface of the 'side plate' to help prevent 'bypass' leakage on the 'side' of the impeller, the 'sides' of the rubber vane should be in contact with metal, not gasket material.