Abstract: An improved "magnetic hook"-promoted catalytic process, catalyst and method of manufacture for heavy hydrocarbon conversion, optionally in the presence of nickel and vanadium on the catalyst and in the feed stock to produce lighter molecular weight fractions, including more gasoline, lower olefins and higher isobutane than normally produced. This process is based on the discovery that two "magnetic hook" elements, namely manganese and chromium, previously employed as magnetic enhancement agents to facilitate removal of old catalyst, or to selectively retain expensive catalysts, can also themselves function as selective cracking catalysts, particularly when operating on feeds containing significant amounts of nickel and vanadium, and especially where economics require operating with high nickel- and vanadium-contaminated and containing catalysts.