340 Static Compression Numbers and Test Procedure
That is race fuel cranking compression territory.
My 340 is about 9.8:1 static compression (iron heads), and with the throttle held open and all the plugs out it cranks at ~175 psi. It runs on 91 octane, but barely. I pulled a couple degrees of timing to make it happy on the street all the time and with the seasonal fuel changes.