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Dry sump vacuum tank

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  • Dry sump vacuum tank

    I have dry sumped my S14 and have a question regarding the breather on the rocker cover.
    I want to know if i can connect a vacuum regulator valve and air filter directly to the rocker cover or whether i need to make a catch tank that has the vacuum relief valve and filter attached to it in case when there is positive pressure in the rocker cover that any oil mist will not spill out of the rocker cover...
    I want to maintain enough vacuum where possible to take advantage of better ring sealing etc but regulate it so that I don't duck in the crank seals etc...
    Anyone else been through this and would share their experiences?

    Thanks Karl

  • #2
    Hi KKO110,
    The rocker cover tube goes to an oil separator down the intake side of the engine, and the oil that is collected there goes down a smaller tube to the connection on the top of the oil pan. The larger tube from the oil separator then goes to the bottom of the log intake manifold where the gas (blowby) is added to the incoming air and any vapors are burned as fuel. The O2 sensor doesn't know the difference between burnt oil or fuel and corrects the A/F ratio as required by the DME.

    I suggest you use the oil separator with your system, what ever you come up with. or you will get unwanted oil in the vacuum tank, which you probably don't want. And you will have to collect the blowby somewhere. So I next suggest that your vacuum collection system should have sufficient capacity to handle the blowby of there won't be much vacuum.


    • #3
      He's wishing to generate some vacuum in the crankcase which he can't do if he use the stock crankcase breather system.

      What you want to do is buy a vacuum regulator and a pressure relief valve that allows pressurized air out at 2psi in case you have a blow by incident. Ideally those two items are connected to the crankcase at the vacuum cover somewhere. Some builders like them on opposite sides of the valve cover but that would require modification to the valve cover on this engine. You might consider welding an AN12 bung to your valve cover or adapting, then run a AN12 line to one of these <> and one of these: <>

      The top of your dry sump tank can be vented to atmosphere to a catch can.

      This is how you do it if you want vacuum in the crank case. Then you have to create a device to measure the crankcase vacuum while running the car on the dyno and set it where you want. Since you probably have mostly stock seals I would suggest not going to high, unlikely that your system can pull much vacuum anyway though.

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