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I realize my engine is different (new LS3), but on mine the "vacuum" connection occurs through a short hose that connects the intake (right behind the throttle body) to the lifter valley. The connection to the valve cover is for make up air -- pulled from the air inlet tube downstream of the mass air sensor - so that the air pulled from the crankcase into the intake manifold to be part of the combustion air is metered. I only need make up air on one side or the other -- the other valve cover vent can be capped.
FWIW
Since the PCV restrictor is in the valve cover for the 5.3L LC9 (I think) -- shouldn't the make up air into the other valve cover come from air inlet tube downstream of the mass air meter instead of from atmosphere (through a "filter")? Won't make up air from atmosphere essentially be a vacuum leak? Trying to learn...
Last edited by Michael Yount; Jul 21, 2017 at 06:50 PM.
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