A little more info. For a 617 turbo the compression specs (at operating temperatures) are given on this page:

http://skinnerbox.steaky.org/Service/W123/w123CD2/Program/Engine/617/01-010.pdf

Normal compression pressure: 24-30 (about 348-435 psi)
Minimum compression pressure: approx. 15 (about 217 psi)
Permissible difference between cylinders: max. 3 (about 44 psi)

Hope this helps.