I was going to ask the same question here. 418 stroker, Auto 3.91 gears. Thermoquad and stock manifolds. 10.5:1. 34 degrees total advance about 8 degrees initial. Starts and runs well EXCEPT when it shifts between gears and pulling hard. Has a bad detonation there that is very worrysome. I have to back it to 30 degrees total to get it to stop, but then it runs really crappy. Using 93 super from Chevron. The former owner said to use the 3:1 mix of race gas, but I drive it a lot and that get tiresome and expensive. So I have to baby it. It was much worse on 92 non ethenol. Hard to understand 1 point octane could make a difference, but I was told that the non gas sits a long time in the station tank and often has much less than shown on the pump.