I highly doubt your motor is 8:1 with 165-170psi compression... The easiest way to determine compression ratio based off cranking pressure is a simple formula... A 1:1 ratio is equal to 0 PSI. 14.7 PSI is equal to a 2:1 ratio. Just multiply your ratio by 14.7 to get PSI, or divide PSI by 14.7 to get ratio.

For example, 165psi / 14.7 = a ratio of 11.22:1 or 170psi / 14.7 = 11.56:1

Mine would be 120psi / 14.7 = a ratio of 8.16:1 or 125psi / 14.7 = 8.50:1

Hope that helps