Just to be sure this is all known: The PCV has 3 'flow' rates.
- Zero flow: With any reverse pressure (manifold pressure higher than crankcase, like heavy reversion pulses up into the intake or a backfire through the carb), the PCV will close. This is due to the check valve built into the PCV. Most guys try blowing through the PCV both ways and find it will not blow-through in one direction; this is the check valve working. This likely what FB is finding.
- Low flow: With higher levels of vacuum in the intake, the PCV is in low flow mode. This limits the the airflow so as to not interrupt idle operation.
- High flow: With low levels of manifold vacuum, the PCV opens to a higher flow rate.
You can't detect the change between high and low flow modes by blowing through it; you can't generate enough vacuum yourself with the low or high flow rates.
OP, what you are seeking is backwards from how PCV's work. They are in
high flow mode at
lower vacuum levels. I am not aware of any PCV that has lower or no flow at a lower vacuum. If your idle is such a low vacuum level, then all you can do is put in a fixed restriction and hope it pulls adequate flow.
With your current set up and adding a restriction (or if the junk box PCV simply has a lower flow rate than a stock Mopar PCV), then you will have:
- At idle, the PCV will be in high flow mode with a restriction
- At light cruise and just off idle, the PCV may switch to low flow mode and still have the restriction
- At heavy cruise, the PCV will be in high flow mode with a restriction
- At WOT, it won't matter as there is little PCV flow anyway
Hope that makes sense!
