340 Demon

Yeah, that's pretty much a no go. I know a guy that does 93 octane with a 12.5:1 hemi but he's an engine builder and has some tricky cam that I don't really understand lol. I've got a 13:1 340 but I have no plans of anything other than 110 for that lol, your kinda pushing the limits of parts breakage with that 91