No problem, Kurt, whatever works for you is fine with me! You can guesstimate the compression ratio by looking at the pressure a compression tester gives- - - -one atmosphere of pressure is 14.7 pounds per square inch, so in an ideal world, a compression pressure of 147 pounds would indicate a 10:1 compression ratio. In reality, there are losses, so you could expect to see maybe 125-130 PSI or so from a 10:1 engine. If the compression pressure on the gauge is down around 110 PSI or less, the engine should run well on 87 octane regular if the timing is set right.
Also, in the real world, compression pressure is affected by cam timing and other factors. Really radical cams keep the intake valve open through part of the compression stroke, so the actual cylinder volume the piston is compressing is reduced. Very radical cam grinds require increased "compression" to get the cylinder pressure back to what a stock engine would have.
Jerry
