408 stroker fuel requirement?

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.

34 total at what rpm? Are you using vacuum advance? What spark plug heat range? What is the coolant temperature?

At your compression ratio you should never ever need race gas at any ratio.

Guys saying **** like that are stuck in the 1980’s. And you didn’t need it back then either.

The only way you might have an issue is if the builder picked a cam that’s better suited for 8.5:1 compression.

Then I’d say get the correct cam.