[Lynn Eades]

I don't fully understand what you are asking. How does the oil get past the camshaft? Often there is a cut out in the cam journal (or a hole through it) and this limits the flow to the valve gear. If the cam is in a certain position there is full flow, and in another position, no flow. The overall effect is a lower psi to the rocker gear (the rotation of the cam being a regulating device)