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Technical Flathead crankcase vent/PCV thoughts

Discussion in 'The Hokey Ass Message Board' started by theHIGHLANDER, Jan 21, 2023.

  1. jimmy six
    Joined: Mar 21, 2006
    Posts: 16,626

    jimmy six
    ALLIANCE MEMBER

    You can get a 90* PVC rubber elbow and use aluminum tubing for most of the line. Keeping rubber line to a minimum and painting the tubing satin or flat black can help hide the system.
     
    theHIGHLANDER likes this.
  2. Beanscoot
    Joined: May 14, 2008
    Posts: 3,528

    Beanscoot
    Member

    I was a bit concerned with that with my setup, but it doesn't cause a dirt build up in the carb. A little oiliness is all, and a quick spray with carb cleaner once or twice a year washes it away easily.
     
  3. Garpo
    Joined: Jul 16, 2016
    Posts: 307

    Garpo

    I have done three flatheads with pvc set ups. First was done 40 years ago . Valve was located along side the adaptor plate I used for a small four barrel. I used a couple of 90' fittings to feed into the manifold beneath the carb, connecting into both sides. I tapped into the manifold forward of the carb to draw from the valley above the gasket.
    I modified the oil filler above the fuel pump to take a gas tank filler cap, with a vent hose below it connected to the air cleaner base.
    Edit; the breather tube at the front of the valve chamber was plugged with a cup type core plug.
    After many years of running this engine was spotless inside - as clean as the day it was put together.
    I used the same set up when I built a new engine. I could not think of a reason to change it.
    Too much time to think, so the flathead for my roadster has the pcv located below the intake, out of sight, again feeding into both side of the manifold. Interesting working around / through the exhaust crossover.
    Carb settings were never a problem. A part turn of the mixture screws was all that was required.
    Not sure if there is measurable vacuum in the crank case, but all three engines have been leak free
    Would I recommend this modification? YES
     
    Last edited: Jan 26, 2023
    joel and kadillackid like this.
  4. theHIGHLANDER
    Joined: Jun 3, 2005
    Posts: 10,581

    theHIGHLANDER
    Member

    Here's why I'm on about doing what im doing. Done, 90% wired and plumbed already. At this point I have no interest in stripping parts off and starting from scratch with a full on PCV system. I'll go on record that my get up won't be the end-all do-all system but it sure will be an upgrade from just open vents. And again the vent by the rt front corner of the engine/pan has adequate oil separation stuff goin on. I can't believe I'm stepping backward. 20210113_195516.jpg
    20210113_195622.jpg
     
  5. theHIGHLANDER
    Joined: Jun 3, 2005
    Posts: 10,581

    theHIGHLANDER
    Member

    Thought I'd check in, didn't give up on this. I didn't have enough steel to do it all, went to copper. I'm half done but other things have pulled me away. I hope by midweek I have it all done and with an assist I'll raise the motor and put it all on. Film at, uh, some day next week...:rolleyes:
     
    kadillackid likes this.
  6. theHIGHLANDER
    Joined: Jun 3, 2005
    Posts: 10,581

    theHIGHLANDER
    Member

    So I whipped up some ½" tubing and made lines for the vent gig. I made it in 2 pcs considering both the desired future for this motor with 2 carbs on an Offy, and frankly the ease of final install as well as occasional service. All of this will be etch primed and painted gloss black. It didn't turn out too hateful;
    20230130_191318.jpg
    I had a couple steel bushings that were just right for sleeve connections. I think they were for disc brakes but the tubing fits them perfect. I'll sweat one tube and let the other slip-fit;
    20230130_191330.jpg
    The only hose I'll need will be well below the exhaust manifold/pipe neighborhood;
    20230130_191417.jpg
    I'm a lazy cheat when I fab stuff. I took an aluminum welding rod remnant and bent it up for fit, and I bent it over the radius of the tube bender;
    20230130_191303.jpg
    So later today I'll sweat the bushings on and make a couple tabs for the bigger tube and bolt that in place. I can share this water pump bolt and one of the plug wire tube tabs;
    20230130_191434.jpg
    Yeah I know. That bolt should be swapped out. Of course I will, its fk'n ugly:eek: and no I didn't put that in there so stop lookin at me like that. Anyways, more later. One of my dearest friends is helping me today so we plan to raise the engine and install the inlet gig from above on the oil pan. Of note, we fired up his Zephyr and noted a light vacuum at idle where his connects to the air cleaner, and it pulls a measured 1" when revved to a cruise RPM. I wonder if a smaller air cleaner will pull more or less, could go either way but my instinct says more. Film @ 11:00 only on the HAMB news network...o_O
     
    Last edited: Jan 31, 2023
  7. theHIGHLANDER
    Joined: Jun 3, 2005
    Posts: 10,581

    theHIGHLANDER
    Member

    Ok, I guess only time will tell. Done, painted and installed. Details, the bushings I eluded to make for nice interference fits without clamps or fasteners. No ½" molded hoses were appropriate for the little bit I needed and the hose connected with no kink anyways. Tested my air cleaner on the Zephyr and it pulls more vac than the stock Zephyr does. Nothing like manifold vacuum but does pull enough to help. Here it is done;
    20230201_185650.jpg 20230201_165253.jpg 20230201_185425.jpg 20230201_165215.jpg 20230201_165206.jpg
    The connector bushing from the longer tube is fixed, sweated that on, the air cleaner tube slip fits into both the air cleaner and big tube. Easy in n out, tight enough to not slip. To review, yes this is not an ultimate system yet but should be an upgrade from just vented to atmosphere. The way this was done it should be easy to rig a full on PCV when the dual carbs get installed, and I can do that work on the bench and simply swap out the manifolds, plug it in.
     
  8. Hillbilly Werewolf
    Joined: Dec 13, 2007
    Posts: 562

    Hillbilly Werewolf
    Member

    Looks great, it easily blends in as factory.
     
    theHIGHLANDER likes this.
  9. theHIGHLANDER
    Joined: Jun 3, 2005
    Posts: 10,581

    theHIGHLANDER
    Member

    It might raise a question now n then. Fun stuff when it does.
     
    Hillbilly Werewolf likes this.
  10. el Scotto
    Joined: Mar 3, 2004
    Posts: 4,721

    el Scotto
    Member
    from Tracy, CA

    I didn't read any of the other responses but this is what I plan on doing...

    hiddenPCV.JPG

    Hidden under the intake and I'll baffle it somehow...
     
  11. Mart
    Joined: Mar 3, 2001
    Posts: 4,989

    Mart
    Member

    Let us know how that turns out, El Scotto. I have wondered how a pcv will work if only tapped into one side of the manifold.
     
  12. theHIGHLANDER
    Joined: Jun 3, 2005
    Posts: 10,581

    theHIGHLANDER
    Member

    So I take it in normal applications that hose end would go to a valve cover or the like? I have 1 aside for later that works opposite, hose end to manifold.
     
  13. hm... i have a plugged source of vacuum on the carb spacer, i wonder if i could grab a PCV (62-64) valley cover and have both a road draft and a pcv?
     
  14. el Scotto
    Joined: Mar 3, 2004
    Posts: 4,721

    el Scotto
    Member
    from Tracy, CA

    It's basically like the 1963 Chevy PCV system except the PCV is screwed into fitting in a tapped hole in a plenum or intake runner under the manifold inside the oil galley. Completely invisible from the outside and simple as can be.

    1963 corvette ENGINE PCV crank-case-vent.gif
     
    Blues4U likes this.
  15. theHIGHLANDER
    Joined: Jun 3, 2005
    Posts: 10,581

    theHIGHLANDER
    Member

    So hose end to vapors on those. Thanks...
     

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