Standard timing was fine when the engines were new and running on the leaded fuels available. Advancing the timing until it pinks/pings will give the best performance, and this setting will vary with the octane rating of the fuel/booster used.
With a manual maggy, Jules' suggestion is an easy and straightforward test. It should experience pre-ignition at some stage, and that's when you're getting close.
Swarfy.
