68 newport VAPOR LOCK

Engine, Transmission & Driveline

  1. 68Newport512

    68Newport512 New Member

    Messages:
    17
    Likes Received:
    2
    Joined:
    Mar 26, 2019
    Location:
    78251
    Anyone cure the vapor lock issue with today's gas?
     
  2. BLUPORT

    BLUPORT Carpe Diem Cras FCBO Gold Member

    Messages:
    1,151
    Likes Received:
    903
    Joined:
    Dec 10, 2018
    Location:
    Eastern NC
    Vapor lock isn't a byproduct of "today's gas."
     
    • Agree Agree x 1
  3. 68Newport512

    68Newport512 New Member

    Messages:
    17
    Likes Received:
    2
    Joined:
    Mar 26, 2019
    Location:
    78251
    Any tips on how to prevent it? After driving for awhile on hot days I get hesitation.
     
  4. HWYCRZR

    HWYCRZR Senior Member FCBO Gold Member

    Messages:
    1,426
    Likes Received:
    1918
    Joined:
    May 13, 2015
    Location:
    Fargo, ND
    What engine, how fresh, is it mostly stock or modified, what Carb?
     
  5. 68Newport512

    68Newport512 New Member

    Messages:
    17
    Likes Received:
    2
    Joined:
    Mar 26, 2019
    Location:
    78251
    383 6.3 stock engine ,new plugs
    stock 2 barrel carb
     
  6. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

    Messages:
    11,391
    Likes Received:
    6363
    Joined:
    May 21, 2013
    Location:
    Marcellus, NY
    That's not "vapor lock".

    Vapor lock is when the fuel gets hot enough in the line to turn from liquid to gas. Most of the time you will get that from sitting and the engine compartment doing a hot soak and the gas in the carb and lines are affected. The car won't start.

    Your problem could be accelerator pump, timing, float level, too lean and on and on.
     
    • Thanks! Thanks! x 1
  7. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

    Messages:
    11,391
    Likes Received:
    6363
    Joined:
    May 21, 2013
    Location:
    Marcellus, NY
    Yes and no. Ethanol laced gas does have a lower boiling point, but really the cause is from something making the fuel lines/carb too hot. It just happens a little easier.

    Winter mix gas does the same thing.
     
    • Agree Agree x 1
  8. 68Newport512

    68Newport512 New Member

    Messages:
    17
    Likes Received:
    2
    Joined:
    Mar 26, 2019
    Location:
    78251
    I did notice if I put in 87 octane the engine will die and won't start back until 30 minutes or so. Then will fire right up like nothing.
    93 octane it wont die just hesitate when accelerating.
     
  9. HWYCRZR

    HWYCRZR Senior Member FCBO Gold Member

    Messages:
    1,426
    Likes Received:
    1918
    Joined:
    May 13, 2015
    Location:
    Fargo, ND
    A couple of easy things to check. To take the vapor lock question out of the picture, but @Big_John is most likely on the right track.
    If you want to minimize vapor lock potential here are some easy things to check.
    First, is your Heat Manifold Valve on your right exhaust manifold opening up all the way? If stuck shut, or only opening part way it will heat up your intake manifold enough to vaporize the fuel in your carburetor. Second, Is your fuel line from the pump to the carb laying on the water pump or intake. The heat from your engine can vaporize some of the fuel in the line. line should not be touching engine.
    Third, does the top of the fuel bowl have a little vent cap or flap that allows the bowl to vent when shut off or idling? Check those simple items first.
    But if it is running and hesitating, start with Big_johns direction.

    Heat Manifold valve
    image.jpg

    Fuel line
    image.jpg

    Carb vent
    image.jpg
     
    • Like Like x 1
    • Thanks! Thanks! x 1
  10. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

    Messages:
    11,391
    Likes Received:
    6363
    Joined:
    May 21, 2013
    Location:
    Marcellus, NY
    That is classic "vapor lock"

    This could be caused by a lot of things, but since you do have some issues with heat (causing the vapor lock) then it would be prudent to start checking some things that are causing excess heat. As @HWYCRZR has suggested, a really good place to start is the manifold valve. Those get stuck and cause all sorts of shenanigans because of the excess heat.
     
    • Like Like x 2
  11. jct

    jct Senior Member FCBO Gold Member

    Messages:
    2,968
    Likes Received:
    1716
    Joined:
    Jun 11, 2015
    Location:
    indianapolis
     
    • Like Like x 2
  12. 68Newport512

    68Newport512 New Member

    Messages:
    17
    Likes Received:
    2
    Joined:
    Mar 26, 2019
    Location:
    78251
    Do I need to replace the fuel sending unit to allow a return?
     
  13. rags

    rags Well-Known Member

    Messages:
    596
    Likes Received:
    275
    Joined:
    Dec 14, 2015
    Location:
    greater norwich metropolitan area
    i run my '65 383-4 on 87 octane pump gas. never a problem. take no precautions storing it over winter and it starts every spring. runs like a champ.
     
    • Agree Agree x 2
    • Thanks! Thanks! x 1
  14. 68Newport512

    68Newport512 New Member

    Messages:
    17
    Likes Received:
    2
    Joined:
    Mar 26, 2019
    Location:
    78251
    I checked the heat manifold valve. Is it supposed to move and spring back? Mine just moves and stays where I leave it.

    20190608_201629.jpg
     
  15. HWYCRZR

    HWYCRZR Senior Member FCBO Gold Member

    Messages:
    1,426
    Likes Received:
    1918
    Joined:
    May 13, 2015
    Location:
    Fargo, ND
    It is supposed to move freely. There should be a spring coil that as the engine heats up it it tightens and moves the butterfly in your Manifold to the open position. When it is cold the valve closes directing the exhaust across the intake to help warm up the engine.
     
  16. HWYCRZR

    HWYCRZR Senior Member FCBO Gold Member

    Messages:
    1,426
    Likes Received:
    1918
    Joined:
    May 13, 2015
    Location:
    Fargo, ND
  17. 68Newport512

    68Newport512 New Member

    Messages:
    17
    Likes Received:
    2
    Joined:
    Mar 26, 2019
    Location:
    78251
    Thanks. I'll pick some up tomorrow. That's my main problem. It doesn't move freely and difinetly wont return back to normal.
     
  18. 68Newport512

    68Newport512 New Member

    Messages:
    17
    Likes Received:
    2
    Joined:
    Mar 26, 2019
    Location:
    78251
    Thank you! The heat manifold valve is the start of my problem.
     
  19. HWYCRZR

    HWYCRZR Senior Member FCBO Gold Member

    Messages:
    1,426
    Likes Received:
    1918
    Joined:
    May 13, 2015
    Location:
    Fargo, ND
    Taking care of that should at least get you started down the right path to help solve some of the vapor lock issues. Spray the heck out of the shaft, springs and try to get some in the little pin holes on the manifold where the shaft runs through. Good Luck