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Technical Ford Flathead Ventilation Problem

Discussion in 'The Hokey Ass Message Board' started by usrrree, Apr 19, 2014.

  1. usrrree
    Joined: Dec 5, 2006
    Posts: 3

    from Missouri

    Well I guess there is a first time for everything. After learning much from the excellent posts in this forum over the years, I now find myself in the position of having to reach out for help with a pesky problem. I am doing a frame off rebuild of a 1940 Ford Deluxe Coupe with a super charged French block flathead. The blower is a Wieand on top of a Cornhuskers intake, and the rotating assembly includes a 4 1/8 crank tied into a Isky 400 Jr cam. The French block is like the early Fords in that the upper half of the bellhousing is cast into the block. Because of this, I had to use the original oil pan from the 40 since it has the lower half of the bellhousing on the back of it. This oil pan is a rear sump and on the front of the pan, there is a small triangular shaped housing that serves as a crankcase vent (similar to a downdraft tube). My problem is that the vent is constantly blowing out oil. I thought at first it was due to the oil pan gasket slipping and allowing oil to pass into the vent from the oil pan, but after replacing the gasket, the problem is still there. This is frustrating since every time I drive the car I am slinging oil all under the freshly rebuilt undercarriage. HELP
  2. flatjack
    Joined: Feb 13, 2007
    Posts: 860


    I don't know French blocks, but the 40 has a tube which extends from a hole in the bottom of the valley which is aligned with the vent to just below the bottom of the intake manifold. This keeps oil form splashing down the vent.
  3. usrrree
    Joined: Dec 5, 2006
    Posts: 3

    from Missouri

    So I pulled the intake today and you are right, there is no vent tube. I pulled the one from the original 59AB but the outside diameter is too big. Does anyone know the correct OD or where I might be able to buy the crankcase vent tube?
  4. HotRodMicky
    Joined: Oct 14, 2001
    Posts: 1,755


    I dont think that will solve the problem......

    You only extend the hole to top of the block
    Pressure stays the same.....

    Buy vern tardels booklet about french blocks...
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  5. jetmek
    Joined: Jan 12, 2006
    Posts: 1,847


    early engines have a vent opening in the pan rail that lines up with the vent box in the pan. 8ba's and French flatties do not . you need to block that opening in your pan with a piece of tin or whatever and I would suggest run a PCV valve in the manifold
  6. Ole don
    Joined: Dec 16, 2005
    Posts: 2,915

    Ole don

    For a PCV to work right, it needs an intake of clean filtered air, and a baffled outlet to the intake.
  7. fenderless
    Joined: Mar 31, 2006
    Posts: 1,280

    from Norway

    French or std. US, you have to take it to consideration that this Flathead is blown. What type of Pistons do you use, forged or cast? Also what type of piston rings do you use. You will get more blowby thus more pressure in the bottom end. I would mound two crank breathers, Offy or similar. Then also as suggested a PCV setup, but I would not suck that oil fumes into the engine. I would mount them at the end of the exhaust headers.
    Just my solution;)


    Last edited: Apr 24, 2014

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