350 Lifter Leak Down

Discussion in 'Small Block Tech' started by Vaughn3031, May 24, 2019.

  1. Vaughn3031

    Vaughn3031 Member

    Does anyone get lifter leak down if the car has been sitting for a few weeks? I get some heavy lifter tick when starting it up after it been sitting until the oil gets to the top of the engine then becomes very quiet .


    Also, non-engine question. anyone know what size speed nut is needed for the 69 GS quarter panel emblems?


    Thanks,
     
  2. Dan Healey

    Dan Healey Well-Known Member

    I do at every startup, however I do have Rhodes lifters which are designed to bleed down at low rpm's...
     
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  3. alec296

    alec296 i need another buick

    Kinda common. Probably the drain back valve in filter. And are you running a oil with zzdp?
    Try a wix or Napa filter if your not using these already.
     
  4. Vaughn3031

    Vaughn3031 Member

    I’m running royal purple with zinc and a k&n oil filter
     
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  5. 1973gs

    1973gs Well-Known Member

    If it bothers you, just try a different brand of oil filter, Growing up, I had two Buicks with 350's and both made that noise at start up after sitting a week or so. It only lasted for 2-3 seconds so I figured that it was normal. It never seemed to hurt anything.
     
  6. Mark Demko

    Mark Demko Well-Known Member

    Its completely normal.
    And since it quiets after oil pressure builds, your perfect!
    Why this happens: Oil pressure keeps the lifter plunger "floating" so to speak, the plunger is down from the retaining ring between .030 and .050 (that's the pre-load) BUT its also NOT bottomed out in the lifter body.
    When the engine is running, and theres oil pressure, the oil entering the lifter body UNDER PRESSURE keeps the plunger from bottoming in the lifter body.
    Valve spring pressure keeps the plunger from "topping out" on the retaining ring at the top of the lifter, so in essence, that plunger is under a "controlled float"
    As parts wear, get hot/cold, your .030/.050 preload is what compensates for the wear of parts, and hot/cold conditions, and that keeps everything quiet, and running normal up to the point that the preload cant compensate anymore.
    When you shut the engine off, oil pressure goes away, and any lifter on the high point of the cam lobe is under valve spring pressure, and that spring pressure will SLOOOOOWLY push that plunger down, its called "leak down" ALL hydraulic lifters have a leak down rate, some more than others, the leak down keeps the oil changed in the lifter:D
    Sorry for the long winded explanation, but its not as bad when you understand how it operates:cool:
     
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  7. Vaughn3031

    Vaughn3031 Member

    It’s my first sbb, have had a few sbc, and bbc, with flat tappet but haven’t had this happen to them
     
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  8. Mark Demko

    Mark Demko Well-Known Member

    The 350 and 455 Buicks have their oil pump in the timing cover, the oil pick up is in the center/ rear of the block.
    On start up, the oil travels from the pan, to the front of the block, thru the pump, then back into the front of the block, so the oil has quite the travel before entering the block.
    The LS engines have a VERY similar oiling system whereas the pump is in the timing cover.
     
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