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Hot Rods Pcv valve question

Discussion in 'The Hokey Ass Message Board' started by Thessler, Jun 24, 2020.

  1. Thessler
    Joined: Jun 16, 2020
    Posts: 5


    I have a 56 ford y block . I removed the draft tube and replaced it with a PCV valve with the intent of reducing small oil leaks.
    It's not working out so well. I think I'm on the right track but need to fine tune.
    I am now getting oil droplets out of the oil fill cap/ breather and the fan is blowing it all the way back to the firewall.
    At an idle When I grab the pcv vacuum hose I can feel the valve fluttering open / shut at pretty high frequency . I'm guessing this isn't normal and maybe the root of my problem.
    I have done a lot of research on these systems and am at a loss on what to do next.
    To much vacuum? To little vacuum ?, Wrong valve (to big or to small ) ?
    Any advice greatly appreciated.
    Thanks , Tom
    dana barlow likes this.
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 46,114


    Hi, it sounds like the PCV valve is probably working ok. Did you connect it in the original direction? pictures would help....

    How worn out is the engine? If it's really tired, you're not going to fix it without an overhaul. If it's in good condition, then perhaps there's something else wrong that is preventing the front breather from doing it's oil/vapor separating job.
    dana barlow likes this.
  3. okiedokie
    Joined: Jul 5, 2005
    Posts: 3,908

    from Ok

    I am a fan of the ME Wagner adjustable pcv valves. Expensive but work.
  4. Thessler
    Joined: Jun 16, 2020
    Posts: 5


    Thanks guys
    I feel the engine is in good shape, no excessive blow by.
    Breather cap is clean and in good shape . I feel like the PCV valve is jumping from idle mode to cruise mode constantly while at idle, I don't know what it's doing at cruise speed.
    Those wagner valves are a little pricey and I don't think that's necessarily the answer.
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  5. Moriarity
    Joined: Apr 11, 2001
    Posts: 18,149

    Staff Member

    did you connect a vacuum gauge? I would be interested in seeing what it reads, Maybe you have a poor sealing valve causing a flutter in the system....
  6. Thessler
    Joined: Jun 16, 2020
    Posts: 5


    Vacuum reads 21 and steady
    Moriarity likes this.
  7. greybeard360
    Joined: Feb 28, 2008
    Posts: 1,466


    PCV valve will flutter at an idle. It will close on acceleration. If your vacuum is dropping below the level that the valve normally closes that could be part of the problem. You could rig a vacuum gauge up to the valve opposite from the vacuum side and drive it and see how much you can accelerate before vacuum drops off. You may just need a different valve.
  8. Mr48chev
    Joined: Dec 28, 2007
    Posts: 26,917


    I don't know how the new "we use less numbers to cover more engines" thing goes with PCV now but they used to be pretty application specific back when. Now that most likely means finding one for the same size engine that you have. = 292 one for a 289/302 theoretically should be right.
    Still even though you don't have excessive visual blow by you may have ventilation issues in the crankcase such as sludge blocking the air flow to PCV valve. If this is a car that you never had the engine apart on there is a good chance that there is sludge blocking the passages for air to the draft tube connection to begin with. That wasn't uncommon back in road draft tube days especially on cars that were mostly driven in town and didn't get a lot of road miles. The crankcase still has to have good airflow for the pcv valve to work. Air in, air though and air out though the valve into the intake.

    Scroll down to post 11 on this Ford barn thread.
    Last edited: Jun 24, 2020
  9. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,675

    from So Cal

    PCV valves are designed to close at high vacuum (idle) open during medium to low vacuum (cruising and accelerating); and slam shut in the case of a backfire. It sounds like your valve is right at the point where the spring is trying to open the valve and the high vacuum is trying to pull it closed, and it's just going back and forth between the two.
  10. KenC
    Joined: Sep 14, 2006
    Posts: 406


    I'm going to face this in the future. Adding PCV to a flat six that doesn't have one. I plan to find a valve that I can take apart. The plan is to change spring tension by adding shims or clipping coils to tailor it to the little 230 with a two barrel.
  11. kabinenroller
    Joined: Jan 26, 2012
    Posts: 448


    Plus one on the Wagner adjustable Valve. I also have a canister installed between the valve and the vacuum source.
  12. Lloyd's paint & glass
    Joined: Nov 16, 2019
    Posts: 2,267

    Lloyd's paint & glass

    I had an oil consumption issue on a late model off topic vehicle, come to find out there was a service bulletin on the issue. Went to the Chevy dealership and got a fixed orifice PCV and didn't burn any more oil. Would one of those help in your situation?
    dana barlow likes this.
  13. dana barlow
    Joined: May 30, 2006
    Posts: 3,892

    dana barlow
    from Miami Fla.
    1. Y-blocks

    Check comp./PSI on all cly//with all plugs out an carb 1/2 open.,see if they are fairly close to each other, or if one or more is off by 20 lbs or more lower. I've had the prob. an found broken rings in my "Y"
    Joined: Dec 14, 2009
    Posts: 2,373


    What Pcv did you use
    Connected to what vacuum ?
    Opposite v/c vented?
    Oil cap vented?
    To be pushing oil out of the vented cap means your building excessive pressure in the engine.
  15. Blue One
    Joined: Feb 6, 2010
    Posts: 10,522

    Blue One
    from Alberta

    Last edited: Jun 24, 2020

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