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Thread: Oil Catch Can

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    Default Oil Catch Can

    Thinking of I installing an oil catch can. Can I run them from both the valve cover and the pcv or will that introduce vacuum issues?

    John

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    Do you mean an oil seperator that gets plumbed back into the pcv system? Or an open to atmosphere catch can with one of those cute little K&N filters on top and a drain fitting on the bottom?
    If you do an open catch can, there shouldn't be a vacuum issue as long as you plug the manifold where the pcv hose went. And both the valve cover and pcv hose can go to the same can.
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    Quote Originally Posted by ZX2.0 View Post
    Do you mean an oil seperator that gets plumbed back into the pcv system? Or an open to atmosphere catch can with one of those cute little K&N filters on top and a drain fitting on the bottom?
    If you do an open catch can, there shouldn't be a vacuum issue as long as you plug the manifold where the pcv hose went. And both the valve cover and pcv hose can go to the same can.
    What he said. Why are you trying to run it this way, anyway?
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    Quote Originally Posted by ZX2.0 View Post
    Do you mean an oil seperator that gets plumbed back into the pcv system?
    Yes. I plan on routing the outlet at the can back into the point where the PCV rubber elbow below the intake is. If routing it like this is not a good idea please let me know.

    Quote Originally Posted by ZX2.0 View Post
    Or an open to atmosphere catch can with one of those cute little K&N filters on top and a drain fitting on the bottom?
    No although I think a drain fitting on the bottom would be a good idea in a sealed system to drain whatever excess blowby gases accumulate in the can.

    Quote Originally Posted by ZX2.0 View Post
    If you do an open catch can, there shouldn't be a vacuum issue as long as you plug the manifold where the pcv hose went. And both the valve cover and pcv hose can go to the same can.
    OK...good to know. If I decide to go atmospheric then I know all I need to do is plug the spot where the rubber elbow goes.

    Quote Originally Posted by Mimino View Post
    What he said. Why are you trying to run it this way, anyway?
    As far as I understand it there are two points where oil vapor gets introduced back into the intake system. The PCV system where it enters back into the intake and at the Valve cover where it is also introduced back into the intake just at a different point. I'd like to eliminate oil vapors getting introduced into the intake gunking stuff up over time. The motor I swapped into the car has over 100,000 miles on it. Even though the cylinders still had some crosshatch and weren't scored I can't say what condition the rings are in without doing a leak test. Granted it may be overkill and I realize that this is more for those that are boosting the cylinder pressure hence more blowby but I would like to install one mainly for piece of mind besides......I got a killer deal on a 3 port mishimoto style catch can!!! 2 input ports and one output port.



    Check me on this please. I plan on running a hose from the PCV valve to the catch can. Does the valve need to be operational or do I hollow it out and use the body more for sealing up the port? My guess is to leave it operational as it meters how much pressure is in the crankcase although from what I've read negative crankcase pressure is what is desirable. If this is so and it won't mess up the engines operation I can go to the JY and grab a PCV and hollow it out. If I can find a good deal on AN fittings then I will go that route but if not then I'll just use some sort of clamp. Maybe a Gates Power Grip heat shrink clamp......

    John
    Last edited by Novanutcase; 04-15-2018 at 07:25 PM.

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    I've never even thought about hollowing out the PCV. I guess it could work ok for the NA guys. I'd leave it stock for FI along with a check valve on the IM side. Subbed for opinions.
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    The PCV valve actually allows a metered amount of air to be drawn through the engine, mix with crankcase fumes & water vapor and introduced back into the intake manifold. There, it's mixed with the fresh incoming air, and burnt off with the next combustion cycle. It's ment to burn off moisture and oil/gas fumes from the crankase so things don't get all rusty and sludgy. If you've ever worked on a pre-1964 engine that was not taken care of, you'll know what I mean.

    The PCV system should be kept intact by putting the oil separator between the valve and the intake manifold. If you gut the PCV valve, you will essentially have a giant vacuum leak.

    The valve cover breather element is basically open to atmosphere, so you can leave it stock or put a little filter on it. Whatever you do, air should be able to flow through it. DO NOT run it to the oil catch can. If that is done, it will create negative pressure in the crankase and no fumes will be evacuated. There shouldn't be any air going out the valve cover element unless the PCV valve or hose is blocked.

    Also, I verified the airflow on my own car by removing the hose to the breather element and placing my finger over the end of it. There was definate suction, and after about 10 seconds a horrible screaching sound started. Sounded like an alternator or water pump bearing about to sieze. Not sure what was going on (maybe air being sucked past a seal), but I don't think these engine were made to be run in a vacuum.

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    Thank you that helps a lot. I wasn't aware that air was drawn INTO the valve cover rather than pushed out. I was under the impression the engine was under constant positive pressure but your diagram makes sense. I thought the makeup air in the crankcase came from the blow by via the intake and once it got to a certain pressure within the crankcase the valve would react metering out just enough air until it was brought down to a certain pressure but, from your diagram, it looks like the makeup air comes from the air entering from the valve cover.

    Is there another outlet of fumes that I would want to filter other than the crankcase? The port I was going to use for the valve cover is now open. If not I'll have to find a plug for it.

    John
    Last edited by Novanutcase; 04-17-2018 at 09:35 AM.

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    I can't think of another place to suck fumes from. In searching, it looks like those 3 port separators are used on engines with 2 banks of cylinders and pull fresh air in through a port in the middle of the engine.

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