Let me add that this is just cranking pressure... It is a rough estimate converting cranking pressure to actual compression.. There are too many variables to determine actual compression ratios based off of cranking pressure... For example a 13 to 1 race engine may only have 100 psi cranking but a stock 8.5 to 1 may have 120 psi. swap cams from one to the other and you might now have 300 in one and 50 in the other.

In any engine an increase in compression ratio will increase cranking psi, but so will increasing valve lash. Decreasing valve lash will increase valve overlap and lower cranking psi. Other variables include rocker arm wear as well as cam wear and advancing or retarding cam timing may have an affect on cranking pressure as well.