Positive Crankcase Ventilation

Manometer Specification:
One inch (1") water pressure at idle to approximately 3-4 inches water vacuum at full load.

Add the amount that the manometer column travels up, to amount column travels down to obtain total PSI/Vacuum.
Example:
One-half inch above zero plus one-half inch below zero equals one inch vacuum reading. (1/2" + 1/2" = 1").