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Discussion Starter #1
289 SBF with FiTech
I've read about the pros/cons of PCV but wanted to get some other opinions. My current valve covers each have a grommeted hole for either a breather or PCV/breather combo.
Should I be running a PCV from one valve cover to a vacuum source in my throttle body/EFI vs manifold? catch can or no catch can?
what's the role of a breather with a port/nipple on it? Is it basically just a breather cap that you can hook a hose up to? where does that hose go? also to a vacuum source or a catch can?
I'm assuming that any positive crankcase pressure just gets vented through a normal breather valve?
 

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Here's a diagram I took a screenshot of off a Google search. PCV or breathers are your choice but, depending on your State regulations, you may require a PCV system for inspection and registration. The breather with the port on it is to connect to your air cleaner. This is the clean air source into your crankcase under most condition and a vent when the PCV valve is closed.

I am running a PCV system but have an air oil separator between the PCV valve and the manifold. Didn't want all the oil mist coating valves and fowling plugs.

HTH

Norm Screen Shot 2020-05-19 at 2.19.10 PM.png
 

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Discussion Starter #3
any breathers w/ PCV built in w/ a matching vented breather so both look the same?
 

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Lots. Do a Google search for engine dress up pcv valve. It all depends on how much you want to spend!
 

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Keep in mind that you’re running fuel injection. The computer wants to know exactly how much air the engine is ingesting. That’s how it knows (among other things)how to set up the fuel delivery .
 

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Discussion Starter #6
Keep in mind that you’re running fuel injection. The computer wants to know exactly how much air the engine is ingesting. That’s how it knows (among other things)how to set up the fuel delivery .
So what are you suggesting? Breathers or PCV? EFI should learn in either situation, right?
 

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Discussion Starter #8
Ok, you guys convinced me. I bought a PCV valve that looks like a breather that will be hooked up to vacuum and another push in round mini air filter for the other side.
next question, my EFI has some vacuum ports on it. should I be using these or directly to one of the intake manifold bungs? planning on street use only. do I need a catch can/oil separator?
 

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In general. PCV is good for the environment, but not so good for the intake system. You are sucking oil vapor in. It can gunk up your intake and of course the intake valves. I would do a catch can.

On the other hand. Open breathers will pretty much guarantee that you always have oily valve covers.

I use a catch can with an open breather on top. But where it comes out of my valve cover, it still makes a little bit of a mess. I can't win.
 

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Not sure where you're located, but in the Peoples Republic of Kalifornia, you're required to have a closed PCV system. PCV to the intake, and if there's another filler neck on the other valve cover, either a sealed cap, or sealed with a tube going to your air cleaner, or at least one stack if running stacks. Not sure how other states are handling it.
 

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If the intake ports are on a single runner than I would move to the base of the throttle body. Too much air/oil in a single cylinder can cause lean conditions and higher wear on that cylinder.
 

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Picture is worth a thousand words two are even better
358868
358869


A pair of valve cover breathers will make you cars lungs smoke free.

NCDMV treats this car as a 1965 for state safety, state emissions & property tax valuation, ($500) max valuation.

Second choice would be my old system

358871


Tubes (Black) from both the breather holes to a oil vapor catch can & out to a road vent tube.

Last choice in excess governmental over-watch states PVC package.
 

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PCV actually helps clear moisture from the crank case. PCV with filtered air source (air cleaner) and a catch can to an an air/oil separator in the line from the PVC valve to the vacuum port would seem to be the best solution for engine longevity AND the environment. We are talking 1968 emissions standards here - the year they went to closed crankcase ventilation. That extra air bleed in does have an effect on the air fuel ratio and needs to be compensated for. Many years ago Chris Richards at MassFlo (now Pro-M Racing) mentioned to me that the PCV is an un-metered source of incoming air and had to be considered in the tune.
Here might be the ultimate PCV valve. Company Bio – M/E Wagner Performance Products
 

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Many years ago Chris Richards at MassFlo (now Pro-M Racing) mentioned to me that the PCV is an un-metered source of incoming air and had to be considered in the tune.
Mark,
So, if you have not gone beyond a standard tune with the original EEC IV computer Ford did or did not consider this incoming air? I do realize that air is not read by the MAF meter. If they did not then its been many car engines with many miles that they've been working, I would assume Okay for many years. Or must this be considered in more advanced tunes for maximum HP/Torque?

I know you may not have the answer to those questions but just throwing it out there.

At the present time I'm hooking up my intake manifold vacuum lines to the PCV valve and other stuff now. There are two I'm hooking up on my '89 Ford 5.0L engine. One from the rear block PCV valve to the upper intake manifold and another from the oil fill on the valve cover to the throttle body. A third gets hooked up to my fuel pressure regulator just for the vacuum and not part of the crankcase system.

George
 

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George, that’s exactly what I have on my engine. I know it’s a sealed system because I can see a difference in idle for a moment when I open the oil filler. Also can feel a slight vacuum when I put my hand over the filler.
 

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The PCV valve prevents or reduces air flow when required to maintain good engine operating characteristics. At high vacuum (like idle) the valve is pulled closed and only a very small amount of air is allowed through. At wot there is no vacuum and the valve closes in the other direction. At these times the breather line on the other side of the engine becomes a vent to allow blow by out of the engine. This is why an open breather, not connected to the air filter, will still oil mist your valve cover at times even if you are using a POV system. In cruise or part throttle operations the valve is open because the vacuum and spring pressure are balanced.
High performance camshafts, with low manifold vacuum at idle, may require a different PCV valve to allow the engine to idle properly. If you have a high performance cam, and can’t get a good tune at idle, block off the PCV valve for a test.
 

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PCV effects on fuel injection vary by system. The FiTech is MAP and it doesn’t care about the “lost air”. As long as it’s relatively consistent to all cylinders it can be tuned for.

MAF is sensitive to lost air so the best bet is to put the breather line back into the airflow behind the MAF and not dump it to atmosphere. Stick shifts may not notice a big difference but my Bronco with auto surged terribly sitting at lights. Moved the breather behind the MAF and it’s smooth.
 

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The PCV valve prevents or reduces air flow when required to maintain good engine operating characteristics. At high vacuum (like idle) the valve is pulled closed and only a very small amount of air is allowed through. At wot there is no vacuum and the valve closes in the other direction. At these times the breather line on the other side of the engine becomes a vent to allow blow by out of the engine. This is why an open breather, not connected to the air filter, will still oil mist your valve cover at times even if you are using a POV system. In cruise or part throttle operations the valve is open because the vacuum and spring pressure are balanced.
High performance camshafts, with low manifold vacuum at idle, may require a different PCV valve to allow the engine to idle properly. If you have a high performance cam, and can’t get a good tune at idle, block off the PCV valve for a test.
Can you please clarify the PCV. Sounds like you are saying the valve closes with vacuum, and also closes with no vacuum.
 

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Mark,
So, if you have not gone beyond a standard tune with the original EEC IV computer Ford did or did not consider this incoming air? I do realize that air is not read by the MAF meter. If they did not then its been many car engines with many miles that they've been working, I would assume Okay for many years. Or must this be considered in more advanced tunes for maximum HP/Torque?

I know you may not have the answer to those questions but just throwing it out there.

At the present time I'm hooking up my intake manifold vacuum lines to the PCV valve and other stuff now. There are two I'm hooking up on my '89 Ford 5.0L engine. One from the rear block PCV valve to the upper intake manifold and another from the oil fill on the valve cover to the throttle body. A third gets hooked up to my fuel pressure regulator just for the vacuum and not part of the crankcase system.

George
If the breather is behind the MAF then the air drawn in from engine vacuum on the PCV has been measured. If an open breather is used or air is drawn from before the MAF then the air is unmeasured.

The open breather can be tuned around. It's effect is most strong at idle or coasting (I think I read that up to 30% of the air at idle can be pulled through the PCV). The reason it causes issues is it creates a weird spot were the adaptive system sees lean so adds fuel but it struggles because the lean condition is localized and it tends to spread the richness to a group of values. One method is to play with the MAF transfer curve to smooth out the low air flow fueling bump.
 

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Here is a screen shot of an explanation of a PCV valve on a Summit Racing Q&A. Basically it’s a balancing act between spring force and vacuum that moves a piston inside the valve and that controls the amount of air flow. No vacuum or pressure the spring wins and closes the valve on the inlet. High vacuum the spring loses and the piston is pulled up against the outlet opening severely restricting airflow. Acceleration or cruise they balance and airflow is high.
The problem we have with higher performance camshafts, with lower idle vacuum, is we can be at the balance point at idle for an OEM PCV valve.

HTH

Norm
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