Fudman,

The best way to look at this is:

1. "A" is the crank case pressure. It is the same whether you measure it at the Top Valve Cover Outlet or the Dipstick because the Top part of the Engine Cam Lobes area connect to the sump via some air channels (this is how crankcase air goes from the sump upward into the cam lobes area).

2. "B" is the Intake Manifold Vacuum.

The following numbers are arbitrary just to illustrate the concept.

Sea level air pressure is 760 mm Hg or 14.7 psi. But let's set this as

__zero as a point of reference __purpose.

And let's say the CCV is designed such that when there is a differential of 3, it opens the spring allowing vapor to return to the I.M.

__Scenario A: car warm and idling at 700 rpm:__
- Atmospheric air "zero"

- Intake Manifold vacuum = "- 1"

- Crankcase Pressure: goes slowly from "1" to "3" (from blow-by)

At "-1" and "1", the difference is only 2, so the CCV is closed, but at -1 and 3, the difference is 4 so the CCV is open allowing vapor to return to the I.M. At the same time, liquid (oil) is allowed to flow back down the crankcase drop by drop (basically dripping, not a full flow).

__Scenario B: you are driving at 3000 rpm:__
- Atmospheric air "zero"

- Intake Manifold vacuum = "- 3"

- Crankcase Pressure: goes slowly from "3" to "5" (from blow-by)

In this case the CCV is always open because the min difference is still 6.

Maybe one of us can get a birthday balloon and play with it this weekend and report back (assuming your CCV is fine)?