Bad wrist pin?

Discussion in 'Gen 1 & 2 - Engine, Exhaust, Drive Line & AC syste' started by LJRuddy, Mar 21, 2009.

  1. LJRuddy

    LJRuddy Pop lock n drop

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    How common is it for the SHO v6 to get a knocking wrist pin?

    My SHO has 170k on it and it is driven pretty hard. Before you ask, the rod bearings are new, the valve train is in perfect order and i know for a fact that it is not piston slap.

    This dull thud (described by me this weekend as a "fapping" noise :lol: ) is coming from cylinder 4. The "fapping" noise disappears almost completely when cylinder 4's plug is removed and is not audible above 1500 rpms.

    This fapping noise seemed to show up all of a sudden one day about 1500 miles ago. The fapping noise has not gotten worse or better even after so many miles driven. In fact, I made a round trip to Lincoln, NE this weekend with this engine. I put about 600 miles on it with multiple high rpm shifts and a highway cruising rpm of 3-4500 for 3 hours each way.

    WTF could this be? I think I might pull the accessory belts off and take some video this week.
     
    Last edited: Mar 21, 2009
  2. zblackbeast

    zblackbeast SHOtarded

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    No.. its Cyl. #4!! I don't think that makes a difference!

    Glad you got tickled by your SHO!

    That noise is very interesting tho.. Try and throw a video up.
     
  3. LJRuddy

    LJRuddy Pop lock n drop

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    Edited... I get confused too easily.

    That was ******* painful. Trying to pull a plug boot off while the engine is running and having it shock you for 45 seconds sucks. :(

    I'll get one up within a day or 2
     
  4. jthod

    jthod Mr. Goodwrench

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    :rofl::rofl::rofl:
     
  5. 93rev2sev

    93rev2sev SHO Member

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    sticky valve? Sounds like you might have a winner. You would have to remove the oil pan again, but you can check that theory out in about 2-3 hours.
     
  6. LJRuddy

    LJRuddy Pop lock n drop

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    How can I find out if I have a bad wrist pin by removing the oil pan? Wouldnt I have to drop the piston?
     
  7. somedude_001

    somedude_001 SHO Member

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    your doing it wrong. when you pull the spark plug wires off you have to make sure that you are not touching anything metal on the car. or you can pull the wire off at the coil and it will shoot a spark to the mounting bolts on the coil instead of you. Please make sure that your left hand is not touching the car if you are using your right hand to work. I recommend keeping the arm you are not using behind your back. Just don't give the spark a reason to pass across your chest and tickle your heart. That is serous business.

    that said it is always funny as hell to hold a plug wire the is not on a sparkplug and touch your friend who is touching the car :laugh_ti:
     
  8. somedude_001

    somedude_001 SHO Member

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    have you considered the possibility of a chunk of carbon on the piston that is slapping the head? when you pull the plug car you shine a light in to look at the top of the piston when it is a bottom dead center so you can see the entire ting.
     
  9. somedude_001

    somedude_001 SHO Member

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    a stuck valve actually sound like the most likely scenario honestly. If it is a intake valve you may be able to see it if you pull the intake and look closely.
     
  10. LJRuddy

    LJRuddy Pop lock n drop

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    Wouldnt a stuck valve cause some sort of power loss? I have none. In fact, I was whooping up on everyone's SHO this weekend at the NEBSHO meet. :munch:
     
  11. 93rev2sev

    93rev2sev SHO Member

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    If you take the oil pan off, you can see the wrist pin, connecting rod and piston. Wiggle the crank. If there's slop in the wrist pin, you should be able to see it or the connecting rod move slightly before the piston starts up/down when you work the crank back and forth.

    You should also remove the baffle. This will allow you to get your hand on the connecting rod. If you take the cap off and rotate the crank out of the way, you can also wiggle the connecting rod from side to side to see if it moves.

    If there's a sloppy wrist pin, that rod bearing is likely to have an interesting wear pattern, too. Like the edges getting more wear than the center.

    It's a sure fire way to find out....but you won't be able to do anything about it from down there.
     
  12. LJRuddy

    LJRuddy Pop lock n drop

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    Well, I am not too worried about it honestly. Not to mention I don't have the time to start digging into my SHO. I was offered a 3.2 with modifications that I was looking for from someone on here. Looks like I might have to purchase it a little quicker than I had wanted. :nut:
     
  13. yamahaSHO

    yamahaSHO E85 whore

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    Bad wrist pin? Highly unlikely. When Pat though he had a bad wrist pin, it turned out to be a spun rod bearing.

    Change your oil, you'll know if it s a bearing.
     
  14. LJRuddy

    LJRuddy Pop lock n drop

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    Well I pulled the accessory belts off to take a video of the noise... Started it up and the ticking was 99% quieter. Put the belts back on, started it up and the noise was back. So I started looking closely at the accessory system. My crank pulley is wobbling like it has a roll of quarters taped to one side. :nut: Found my "bad wrist pin"
     
  15. zblackbeast

    zblackbeast SHOtarded

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    lol.. figures..
     
  16. JRA2000TL

    JRA2000TL The Complainer

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    Mine makes the same noise from cyl #4; crank pulley doesn't wobble though and noise isn't from the lower end around the bearings.
     

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