I am unaware of the values for a cold test. The reason for the hot or rather warm test is that the metals naturally espand with the heat and this is actualy your true compresson when running I believe.
I could also be wrong but makes sense to me.
I think your numkbers are a little low but the 315s arewithin spec. I would be concened about the 290 cylinder but again since this was cold that may not be a bad number.

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique