I have a small Moroso oil separator installed in in the PCV system on my truck just like the one shown below.

I have a hose going from the drivers side PCV valve to the canister and then from the canister to the intake manifold vacuum port. The passenger side valve cover PCV port and the port on the TB are capped off. I have a real strong vacuum pull on the oil fill cap when the engine is running when I attempt to take it off. Is this normal? I originally had the passenger side PCV port "T"d into the drivers side hose going to the canister but the the vacuum was so strong it affected the idle so I was told to remove that "T"d hose and just cap those ports. I still have the strong vacuum but it doesn't affect idle now when I break vacuum by removing the oil fill cap when running. Just making sure this is normal. I know race engines with vacuum pumps sometimes require relief valves.

 

You need to open up the passenger side to the atmosphere. You can put a filter on the oil cap or attach a hose and filter to the tube on the valve cover. Right now you have no fresh air coming into your engine.

 

Correct me if i'm wrong but when it was hooked up originally it also didn't have fresh air coming into the engine. Passenger side port went to the TB and the drivers side PCV valve went right to the intake port. I just remember not having so much vacuum behind the oil fill cap when hooked up the OEM way. Thinking of putting a small brass breather on the oil fill cap like those used on rear end housings in race cars.

 

From the factory the engine got clean air from the intake tube after the air filter and it went into the passenger valve cover.

 

Not questioning your knowledge at all but I've had a K&N cold air kit on this for years now and I don't remember it having any tube from the OEM intake tube to the valve cover and if it did where did it go into the valve cover? There are no capped off ports on the VC for one. Just trying to gain more insight.

 

The factory one drew from the port on the TB, which is in front of the blade and doesn't see vacuum.

With your current setup, you need to install a restrictor to the vacuum source to limit the pressure. Factory setups do this using a PCV valve or with a fixed orfice port. Or if you are wanting a high performance engine that makes more power than stock I recommend running a vented catch can to relieve crankcase pressure.

 

This is what I have and I ended up doing.
I put a small brass breather on the oil fill cap. It pulls about 5 inches of vacuum at idle thru the breather which is ok. If I hook the crossover hose back up it pulls almost 15 and changes the idle speed so I'm leaving it like this.

 

Hmmmm.....my passenger valve cover has a bung just past the fill cap on the intake side. i capped mine off and put a screw in filter in place of the oil fill cap

 

My pass. VC has a port just behind the oil fill cap that you might be able to see if you look close enough. It has a black vacuum cap on it right now. But it use to have a hose running from it to a port on the TB up on the opposite side of the IAC. That port is also capped. I just seen a place that makes a breather to take the place of the oil fill cap.

 

How hard headed are you. The TB port IS in front of the throttle blade and is a fresh air source for the pass side valve cover port. It provides filtered air to the crankcase to replace dirty air pulled out of the drivers side valve cover.