Polymer blends are mixtures of at least two macromolecular species, polymers, and/or copolymers. A good blend should have strong interphases between different parts of the constituent polymers. To improve adhesion and miscibility of EPDM and SBR in their blends, a Lewis acid, AlCl3, was used to form EPDM-g-SBR copolymer through Friedel–Craft reactions. The effects of blend AlCl3 content, the diene monomer content of the EPDM, the EPDM–SBR weight ratio in the blend, the room temperature aging of the blend, and the type of the oil in the blend on cross-link reactions were studied. The results showed that an increase in AlCl3 content, up to 2 phr in the formulation, was beneficial to ΔTorque (difference between minimum and maximum torque in cure trace) and cross-link density (CLD) values of the compounds. The viscosity of the blends played a key role on AlCl3 curing of the compounds. As a general rule, the ΔTorque and CLD values tended to increase with diene monomer content of the EPDM. A high reduction in ΔTorque values was observed after 3 months of aging at room temperature. The oil incorporation was beneficial to cure parameters in the following order: oleic acid, paraffin oil, no oil, and aromatic oil, respectively. The EPDM–SBR weight ratios of 50:50 and/or 60:40 were demonstrated to be desired blend ratios.