I currently run a 440 with 10.15 to 1 compression with 915 iron heads in my street car with no problems at all on 92 octane fuel. The piston's however are forged Weisco's and not the half and half KB's. Timing stays at 37 degrees and I run the MP 284 cam. I have ran 110 on the strip with no performance gain at all. As someone else stated, it depends on the cam and how much compression will be bled off. I have to believe that anything under 250 duration at .050 is gonna bleed enough compression to allow you to get away with up to 10.50 to 1 on 92 octane. Also, the timing shouldn't be dialed in too low either. This is based on what I know and have implemented.