Compression ratio too high for 91 octane?

I'm with RustyRatRod on not jumping to conclusions without more details. Without the dynamic CR, how can anyone answer the question with certainty? One crucial factor that I haven't seen mentioned, unless I missed something reading through the thread, is the OP's elevation, which impacts cranking compression and therefore dynamic CR.

I take it that people claiming that 11.8:1, iron heads, on 91 octane is impossible have never bummed around the pits at Bandimere Speedway. Here in Denver at 5,600', the elevation robs us of approx. 15% cranking compression versus sealevel, and that's with a less aggressive cam. Add more cam overlap and the dynamic CR gets skewed further. 11.8:1 here would have a dynamic CR that acts more like 10:1 at sealevel, which is certainly doable on 91 octane. I beat on a 383 with 11:1 compression, iron heads, 91 octane. No issues. I wouldn't have any hesitation trying for 11.8:1 if someone wants to buy me the pistons, cam, and converter:D Not everyone lives at sealevel.