Stroker 340>416 Build Advice
I don’t have 91, just 93’or 89. So my experience is zero with that octane. For WIW, I run 93 on a 11.4-1 - 360 with the TF heads and flat top pistons at zero deck. The cam is small, which causes cylinder pressure to rise vs a larger cam. It’s 224@050, a Hyd roller.
Perhaps someone in your neck of the woods can say better. It’s all about the cylinder pressure the engine develops.
IMO, not a fact, but with the 241/247 cam used by Blue Print in the 408 stroker in the videos which are filmed in Cali, a max 91 octane state, it’ll work. Does altitude have an effect? To your benefit I think.
You can make a small adjustment to the final compression ratio with a thicker head gasket.