So here's the deal. I'm about to rebuild my 455 olds and I'm wondering what compression ratio I should shoot for. In my part of NW Iowa, it's hard to find anything higher than 91 octane (unless I wanted to convert to e85). I was thinking that I would be safe at 9.5-1 CR but then a guy at work said that he runs 91 oct in his 10-1 cr Pontiac 455.
So what do you guys think? Could I go 10-1?

 

There's no hard and fast rule. Depends on the head material, piston/head chamber shape, plug heat range, cam profile, timing curve, altitude, rear end gears/tire, etc etc.
In general, aluminum heads seem to do fine around 10:1, sometimes higher, sometimes lower. Iron tends to do fine around 9:1, sometimes higher, sometimes lower.

IMO, it's not worth sweating over a specific compression ratio unless you have some very specific goals. And if it ends up pinging, then back off the timing and/or keep a few jugs of race gas handy to mix in.

 

I agree with the above.

From what I have learned, the cam intake closing events can make a huge difference in cylinder pressure (dynamic compression ratio) and can make two engines with the same static compression ratio function very differently. So you could get away with 10:1 but you would need the right camshaft profile (and overall tuning).