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56 Y-Block 312 crankcase ventilation

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  • 56 Y-Block 312 crankcase ventilation

    Can anyone give me direction for adding PCV to my 56 312 Y-Block? Id like to eliminate the draft tube if possible. Can the draft tube outlet be plumbed through a PCV valve back into the carburetor or intake manifold? Would I need an oil separator can?

  • #2
    Check out this link in the Technical Resource Library showing the alternate method. No oil separator is required. Although it pertains to a 352 it will work the same on a Y block.

    John Pizzi - Squarebirds Administrator

    Thunderbird Registry #36223 856-779-9695


    • #3
      Y-blocks have a valley pan that differs from an FE. Yes, you can certainly add a PCV instead of the draft tube BUT... How much blowby are you getting? If it's excessive, no system will help. Every engine needs proper ventilation. If the intake causes negative pressure (a vacuum) in the block without proper ventilation, an added PCV will actually promote more blowby.

      45 crosshatch in the cylinder walls prevents rings from hydroplaning over the oil. Shiny cylinders burn oil and cause plugs will foul. Yes, worn rings also contribute because they don't exert as much pressure to scrape the oil off the cylinder walls. Crosshatch works just like those grooves they cut into the road. It gives oil somewhere to go. So, worn rings and shiny cylinders cause lots of oil consumption. You really don't want that going in your intake. When your Y-block was new, the draft tube was acceptable. As the engine ages, more fumes mixed with oil stink and drip on your garage floor.

      Under your draft tube (in the valley cover) is a 'box' with wire mesh that is supposed to coalesce oil from the fumes and send it back to the oil pan. You can see the space in my first picture.
      Since the valve covers are closed, If you convert the draft tube hole to a PCV, the oil filler cap MUST BE VENTED to allow fresh air in. That will prevent a vacuum situation.

      I'm sure you have more questions so fire away. - Dave
      My latest project:
      CLICK HERE to see my custom hydraulic roller 390 FE build.

      "We've got to pause and ask ourselves: How much clean air do we need?"
      --Lee Iacocca

      From: Royal Oak, Michigan


      • #4
        CASCO has a PCV conversion kit available for under $60.


        • #5
          Thanks for the responses. My engine has the draft tube with a canister filter, that exits the front of the block on the passenger side, in front of the oil filter. The valley pan does not have an outttlet for a draft tube. The oil filler cap is vented but not currently plumbed to the air filter. I dont think that I have excessive blowby, but I do smell exhaust fumes in the cabin, as well as in the garage after driving the car. The engine doesnt use oil between oil changes, or smoke under load. All 8 cylinders had good compression when tested. Minimal oil drips from the draft tube. It has a Quick Fuel carburetor which has an unused vacuum port in the rear. The intake manifold also has an unused vacuum port behind the carburetor.

          Is is it possible to plumb the draft tube outlet to the carburetor vacuum intake, with an inline PCV valve? Or will I have to replace the valley pan with one which has an outlet for crankcase ventilation, in order to add a PCV system? Id prefer not to have to pull the intake manifold if I dont have to.