This link given by 4V & Proud in another post is very interesting and indicates how to estimate the pressure in the cylinder at the cranking speed:
http://victorylibrary.com/mopar/cam-tech-c.htm
To do the math you need to know the stroke, the bore, the length of the connecting rod and the angle of the Intake Valve Closure.
But very roughly, it's between 10 and 15 bars
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