The octane selector is just another way to adjust the timing. Once you set the timing by loosening the hard-to-reach screw behind the distributor, you can make minor adjustments to the timing with the octane selector. It was designed for making adjustments if you were to fill the fuel tank with gas of differing octane than what you originally set the timing for. The octane booster bracket has reference marks to allow you to return to the original timing setting without needing a timing light. For your purpose, it is a great feature to quickly troubleshoot your possible timing problem without using a timing light.
