Wristpin knock.

Discussion in 'Chevy Truck Forum' started by UncleBigBad1968, Oct 15, 2012.

  1. UncleBigBad1968

    UncleBigBad1968 Senior Member

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    Hello all.... I got a buddy who has a '90 k1500. The 350 got real hot once over summer, due to a Bad waterpump. It lost power and rattled to a stop. Found out it was outta water. Anyway last week the weather got cod, close to 33 deg and the 350 it started to knock the same morning, like a loose wristpin. Bein as he doesnt have the money to replace it yet, he wants to know how long it might last just driving it as a normal daily driver? I think its a wristpin, because it has the double knock. Oil pressure is good around 40psi. Vibrates a bit about 2krpm. Just like to have a good guestimation, he is going to bide his time until he could afford another 350. Thanks
     
  2. chevychase

    chevychase Semi-Admin
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    If it is a wrist in it will have more of a loud ticking/scraping sound. Sounds like a rod to me. If it is a wrist pin it will scratch/score the piston wall.
    Tear up jack.Will not last long.. It will start smoking bad. If it is a rod.tell him to keep 5w-30 in it..cold weather..oil will be thinner at start up.
    I had a rod knock at cold start ups on older trucks never did give out .
     
  3. leolkfrm

    leolkfrm Full Member

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    may have taken out some rings...will knock like a diesel...might be worth rebuilding once you confirm the problem
     
  4. UncleBigBad1968

    UncleBigBad1968 Senior Member

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    So far no smoke. Doesnt knock all the time, just at low idle.
     
  5. chevychase

    chevychase Semi-Admin
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    Sounds like a rod to me...use thin oil.
     
  6. Case 7230

    Case 7230 Senior Member

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    Wrist pin noise very distinctive. Best heard at idle. Usually a sharp, metallic, DOUBLE knock. Can have engine at idle and short out plug on suspect cyl, noise will usually increase.
    Can retard ign timing to reduce severity.
     
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  7. UncleBigBad1968

    UncleBigBad1968 Senior Member

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    Ok sounds like a def wristpin. Only hear it at idle.
     
  8. truckabuser1

    truckabuser1 Senior Member

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    If using thin oil might be a rod bearing that's worn... Slow idle thin hot oil with worn bearings is asking for trouble

    My vortec did that. 530 destroyed that engine faster and faster as stuff got more worn and dropped more pressure.

    I'd drop the pan and roll in new mains. (roofing nail in crank to help roll out top bearing, might have to make it fit by bumping it with a hammer gently, and they only roll out ONE way) and stuff in new rods.... Easier then pulling top apart with the price of gasket kit....
     
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  9. truckabuser1

    truckabuser1 Senior Member

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    #2 and #8. Caught it in time. Both too far out of spec and had to get crank turned.....

    Tight bearings and 15-40 year around. Dude holds 65psi @200F now. No more almost 5psi at idle hot in gear...
     
  10. UncleBigBad1968

    UncleBigBad1968 Senior Member

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    Got mixed info.... Thin or thick oil? Chevychase...... You trying to ruin me?
     

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