Bottom End Knock

Discussion in 'Engine Topic' started by WiggyB31, Apr 3, 2020.

  1. Rustbucket350

    Rustbucket350 Veteran Member

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    And which bearing/what bearing would that point to?
     
  2. Rustbucket350

    Rustbucket350 Veteran Member

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    Vibration and a knocking sound. That would lead me to loose motor or trans mount on a 4 speed vehicle. If you've already checked that you should have checked the flywheel and clutch.
     
  3. Rustbucket350

    Rustbucket350 Veteran Member

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    if the flywheel and clutch checked out fine and so did all your mounts you MIGHT have a knock in the motor.
     
  4. BuzCrz

    BuzCrz New Member

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    I run Amsoil Z-Rod oil in my 350 crate motor. Older type motors need zink in the oil to prevent wear, particularly camshafts. Don’t know if this would explain the wear in your case....
     
  5. Mike Sinkoski

    Mike Sinkoski New Member

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    You can isolate a rod to a common journal or a specific cylinder by pulling spark plug wires with engine at a idle, ifit doesn’t change the knock it ain’t a rod. Also in addition to the mentioned fuel pump and flex plate, a water pump can knock, and a exhaust header banging on the chassis can make that rapping sound.
     
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  6. Jfair

    Jfair New Member

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    A blown header gasket will sound like a rod knock also. I thought I had thrown a rod after going down the track.
     
  7. oldchev

    oldchev New Member

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    Just like rustbuctet350 says,
    Can be most anything and being none of us heard it or was there, we are all just benching it on the forum. Good fun, little results.
    You have a plan to inspect the bottom end, see where that goes. IF...a bearing has been chewed up even a little the material will have traveled already so a tear down for cleaning will be necessary to ensure future longevity, beside correcting this problem. Most of the time on low mileage engines a bearing failure indicates some other problem so the -why- must be discovered. Maybe its something else.
    Please let us know how this turned out.
     
  8. 1980RS

    1980RS Veteran Member

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    I have a flat top 406 I am going to run this year and it has some knocking noise mostly cold, changed out rockers as it sounds the same as my kid's old 350. I bought this thing for $100 so did not expect much, this time i did not check the piston to wall clearance and that may be the reason it's noisy. Holds great oil pressure, just going to run it, loose engine go fast. May not last long but boy what a ride.
     
  9. budro6968

    budro6968 Veteran Member

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    Piston slap when cold. Warms up things expand goes away.
     
  10. Rustbucket350

    Rustbucket350 Veteran Member

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    Piston slap can be a major cause of this issue on motors that are either high milage or rebuilt. Pulling the plug wires won't do anything because the rods will still rotate as long as the engine is moving.
     

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