PCV routing? How to NOT have oil in your air filter

[hatchsub]

Hey just wondering if anyone has any suggestions of how to route the PCV valve hoses so that i dont get oil in my air filter housing. I have a weber carb and routed the tubing similar to how everyone else on here has. I have both valve covers connected by a tube. Then i have a tube coming up from the PCV to that main tube. Off of this tube i have one running up to the carburator air box. Is there a better way of doing this? I was told this is the normal way of hooking up the PCV since it mimics the factory routing.

[bobjr94]

I have one valve cover connected to the port in the air cleaner, and the other valve cover to the pcv valve. This is not the factory routing on this kind of subaru but cut my oil blow by way down. I use to always have an oil film or sludge getting blown into the filter or housing.

 

This is the configuration used by most v-6 or v-8 engines, one side mainly in, the other side mainly out and seems to work well on my ea81 brat. Under high rpms or if your engine is worn out you still may get blow-by into the filter but most of the time what ever makes it up the tube will be sucked into the pcv valve and not plug up your filter or get into your carb.

 

You can also get inline oil separators, that cut some of the blow-by out. Some turbo cars have them, but they are also on newer escorts and theres tons of them in the junk yards.

[mcbrat]

Hey just wondering if anyone has any suggestions of how to route the PCV valve hoses so that i dont get oil in my air filter housing. I have a weber carb and routed the tubing similar to how everyone else on here has. I have both valve covers connected by a tube. Then i have a tube coming up from the PCV to that main tube. Off of this tube i have one running up to the carburator air box. Is there a better way of doing this? I was told this is the normal way of hooking up the PCV since it mimics the factory routing.

 

that's the right way. how are you connecting to the airbox?

how is your pcv valve?

[Andy FitzGibbon]

What year/model is your car? Hooking up both valve covers to one hose isn't the right set up for an EA82. I don't know if 81s or 71s are set up different or not.

You want the air to flow across the crank case which it can't do if you have both heads hooked to a common hose. Haynes and Chilton manuals both have the factory PCV system diagram that illustrates how the system should work.

Here's a description of how the PCV system works from an old thread:

 

Hooking both valve covers up to a single hose defeats the purpose of the PCV system. The intent is for clean air to be drawn into the passenger side valve cover and head. The air mixes with blow by gasses as it travels across the crank case, then exits through the driver's side head and is routed back into the engine. In conditions of high manifold vaccum, the PCV valve is held open by vaccum and the air/blowby mixture is pulled into the intake manifold for recombustion. When manifold vaccum is low (such as a wide open throttle condition), the PCV valve closes and the air/blowby mixture is routed into the intake duct (SPFI) or air cleaner (carb) for recombustion.

There really isn't any reason to eliminate the system. The only reason I can think of is that if your engine has extremely worn rings, the system usually won't function properly due to high crankcase pressure. The whole system becomes a crankcase vent, rather than a "flow-through" system as the manufacturer intended, and you end up with lots of oily blow by in your intake duct (or air cleaner on carbed models). The same symptoms will occur on an unworn engine if the PCV valve is stuck or broken- blow by will be routed to the air cleaner/intake tube at all times and will leave an oily mess.

The old time trick for worn out engines is the way the old cars did it, with the "venturi tube" mentioned above (although the venturi effect isn't really necessary with the excess crankcase pressure of a worn engine). The "environmentally conscious" method is to vent the valve covers directly into a plastic bottle, which you occasionally empty.

As GD mentioned, having a properly functioning PCV system helps keep the oil cleaner by removing acidic gases from the crankcase. This won't happen if you put a little filter on each valve cover or run both valve covers into a single hose, and will only happen to a certain extent if you run venturi tubes.

Andy

[hatchsub]

that's the right way. how are you connecting to the airbox?

how is your pcv valve?

I just have a T fitting from the PCV up to to bottom of the airbox. Im getting some oil in the carb air cleaner. My engine is no where near worn out being that its only got 73,000 miles on it. My car is an 83 subaru with an EA81. Sorry should have mentioned that

 

PCV valve is an aftermarket NAPA one that i installed about 2 years ago now. Could that be the cause of it all? Ive heard that factory is the only way to go with these little things.