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REBUILT 1940 Pontiac 6 CYL Flathead

Discussion in 'The Antiquated' started by Paula Borneman, Jun 28, 2019.

  1. Paula Borneman
    Joined: Apr 5, 2016
    Posts: 5

    Paula Borneman
    Member

    Hey Folks,
    Now I know that you all have gone over the standard overheating of the flathead a million times. However, here is the problem.
    Freshly rebuilt 6 cylinder flathead (from reputable builder)
    New radiator
    New - thermostat, hoses, pumps, you name it, it's new.
    Timing is advanced 4 degrees
    It's STILL overheating starting at idle???? Any idea where to go on this? We have tried just about everything from a water treatment to changing the oil on this thing.
    And while your at it, we picked up a vibration?? (flywheel & clutch assembly were both balanced)
    You idea's are welcomed!!
     
  2. Bird man
    Joined: Dec 28, 2009
    Posts: 895

    Bird man
    Member
    from Milwaukee

    New thermostat faulty? lower hose collapsed, gusher tube damaged or not present. Too much hydrazine blend in fuel :D This in not new technology, the answer is merely eluding you.
    Viva Los Ponchos!
     
    Paula Borneman likes this.
  3. Paula Borneman
    Joined: Apr 5, 2016
    Posts: 5

    Paula Borneman
    Member

    Thank you- gusher tube is in good shape. Gusher tube came out/in - in 1 piece. We'll keep looking.
     
  4. tractorguy
    Joined: Jan 5, 2008
    Posts: 894

    tractorguy
    Member

    Is it overheating based on gauge reading or actually showing overheating signs.....snap....crackle....pop....radiator pressure......steam etc. ?
     

  5. Paula Borneman
    Joined: Apr 5, 2016
    Posts: 5

    Paula Borneman
    Member

    The full kaboom... on idle. We are also running the heat gun on it.
     
  6. Rickybop
    Joined: May 23, 2008
    Posts: 9,606

    Rickybop
    ALLIANCE MEMBER

    Back to basics.
    Water flow
    Air flow
    When the engine is cold, run the engine with the radiator cap off. As the engine warms and the thermostat hopefully opens, watch for a good flow of water flowing past the filler neck.
    That's a start.

    Sent from my VS835 using The H.A.M.B. mobile app
     
  7. Paula Borneman
    Joined: Apr 5, 2016
    Posts: 5

    Paula Borneman
    Member

     
  8. RidingMechanic
    Joined: Jul 31, 2017
    Posts: 96

    RidingMechanic
    Member
    from Cincinnati

    Do you have the correct head gasket? I don't know the pontiac sixes very well but maybe there are a couple variations with different steam/water holes?

    Is it the correct head for that block and is it the correct thermostat housing? Is your water pump turning the right direction? Just a few thoughts...
     
    tractorguy likes this.
  9. tractorguy
    Joined: Jan 5, 2008
    Posts: 894

    tractorguy
    Member

    Just to reiterate several other comments......is the waterpump turning the correct way ?......Is the impeller on the waterpump correctly ?......Is impeller slipping on waterpump shaft ?......last but not least.....is there a head gasket problem that is allowing combustion pressure to enter the cooling system directly ?

    Can you remove one or all sparkplugs one at a time .......devise insert for plug hole (store bought or break spark and braze air fitting to plug body)......put air in each cylinder.....watch for bubbles in radiator.
     
  10. Brizo
    Joined: Jan 15, 2011
    Posts: 222

    Brizo
    Member
    from Indy

    Paula, the last few posts are exactly what you need to check! Something you are taking for granted is not right. I've been driving one for 50 years and those engine were tough as nails and never had any tendency to overheat. Good luck
     

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