Need Help With Evac System

Discussion in 'Superchargers, Turbos, Nitrous' started by Unforgiven, Mar 6, 2020.

  1. Unforgiven

    Unforgiven solid fixture here in the forum

    Looking for a way to vent the crankcase on an old school SBC with a blower on top.
    The engine has open headers.
    My idea was to run a line from the bolt hole that holds the fuel pump rod from falling out, to a catch can mounted on the firewall , and then to the collector on the header. I have borrowed a pic from the web to try and give a visual for what I am thinking. Do you men think this would work , or do you think it would suck to much oil from the case. There is a fuel block off plate on my motor.

    1024px-Chevrolet_small-block_engine_-_Automobile_Driving_Museum_-_El_Segundo,_CA_-_DSC01736 (1).jpg
  2. Indycars

    Indycars Administrator Staff Member

    It's more complicated this way, so I have to ask .... what makes this better than pulling vapors
    from the valve cover ?
  3. Unforgiven

    Unforgiven solid fixture here in the forum

    I dont have pics yet Rick, but the covers I have only have one threaded hole on the front face for a breather.
    Also, I was thinking that the pressure in the crank case will have to travel up through the pushrod holes to exit out the covers. Might be splitting hairs... but... it is just an idea. I need to vent this motor somehow.. It kept blowing the dipstick out on the dyno, and the valve cover hole was open to the air. I thought that the bolt hole for the fuel rod would get the pressure out quicker from the crankcase.
  4. Indycars

    Indycars Administrator Staff Member

    OK, I understand your thinking now.

    Looks like you could try it and if you don't like it, it would be easy to add more area for breathing
    thru the valve covers and remove the fuel pump rod connection. I know it wouldn't be hard for you
    modify the valve covers for more breathers.
  5. Unforgiven

    Unforgiven solid fixture here in the forum

    Thanks Rick... The holes in the front face (there not on top like normal) are tapped for a -12an bulkhead fitting. My plan was to mount a 90 degree fitting on them and mount a breather on each cover. Then I would connect a -6an 0r -8an line from that bolt hole near the fuel block off plate. I figured that if I ran the tube up and over the intake... it would allow some of the oil to drain back while still allowing gasses to evac to a catch can (unvented) then run down the firewall to the collector. I also have a fitting on that Canton oil pan that I could vent from also.
    I really don't want to drill any holes in my new billet valve covers.. :eek:
    As you already know.... I have had a bout of bad luck modifying valve covers.:rolleyes:

    Now that I think of it... I could modify a block off plate to except a -12an bulkhead fitting and allow more area for gasses to escape. I don't think it would be that hard to make a baffle behind the plate.

    Below is a pic of where I mentioned a spot I could plumb a tube up from and install a breather cap.

    Please note that these are not the valve covers I am using.

  6. Unforgiven

    Unforgiven solid fixture here in the forum

    Grumpy.... Do you ever remember guys venting from the pan back in your racing days?
  7. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

  8. Unforgiven

    Unforgiven solid fixture here in the forum

    Yes. That is the system that I have and am installing.. But I am not understanding where the fresh air is entering .
    I am thinking that yes it will relieve pressure, But how are the gasses and condensation being moved out with out a source of fresh air to replace them.
  9. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

  10. Unforgiven

    Unforgiven solid fixture here in the forum

    I went out to the barn and got a few pics of what is going on.

    Here is one of the new valve covers. notice how there is only a threaded hole in the front face.


    Below is what I had in mind for the evac system.
    Now. the breather caps do not have the ability to draw air from underneath themselves as
    your second pic shows Grumpy. What I was thinking was: I do have one of those edelbrock breathers,
    and I was trying to incorporate it into the system along with the evac system.

    My thought now is to draw fresh air into either the pan or the fuel block off plate, using the edelbrock breather, and let the headers pull
    from the valve covers as shown in the pic below.

    What do you think...


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