Wrist pin noise

Discussion in 'Classic Buicks' started by suntreemcanic, Feb 20, 2022.

  1. suntreemcanic

    suntreemcanic Well-Known Member

    I know this question is going to open up a lot of ideas about my mechanic abilities but I am hoping someone has a diagnostic method I have never heard of before. Does anyone have an idea about diagnosing which cylinder the wrist pin noise is coming from? Pulling spark plug wires, wooden dowels and automotive stethoscopes do not isolate the location of the noise. Crankshaft was turned to .020 under and both mains and rods were plastigauged (sp) before assembly. Egge pistons, about 4,000 miles. Good power no blow-by the engine runs great I hate to tear it completely down looking for the loose pin. I am hoping someone has an idea I have never heard of.
     
  2. sean Buick 76

    sean Buick 76 Buick Nut

    Pull the oil pan off and turn the engine back and forth to find the issue.
     
  3. Jim Weise

    Jim Weise EFI/DIS 482

    Are you sure it's a wrist pin?.. I assume it has the trademark "double tap" knock noise..

    In racing, we run wrist pins up to .005 clearance, so they have to be really loose before they start making noise. Usually this is caused by galling due to a lack of oiling.

    The noise did not change when pulling plug wires at idle, try it again, but this time put some load on the motor.. Set the parking brake/block the wheels, have an assistant put the trans in gear, and brake lock it to 12-1500 rpm during the test.

    JW
     
  4. suntreemcanic

    suntreemcanic Well-Known Member

    When I put it under load the noise goes away. Pin clearance is what ever Egge made it. I never measured pin clearance before I assembled it. The noise is louder now that it was 2,000 miles ago according to my wife. ( I do not hear very well.)
     
  5. John Codman

    John Codman Platinum Level Contributor

    I have heard sloppy mechanical fuel pumps that sounded a lot like a bad wristpin, but I assume that you replaced the fuel pump when you had the engine apart.
     
    66electrafied likes this.
  6. 66electrafied

    66electrafied Just tossing in my nickel's worth

    Had exactly that happen on a freshly rebuilt Ford 390; - the fuel pump eccentric had a sleeve bearing was made a little too loose and it knocked against the timing cover. 5 minutes with a grinder to machine that face down the required 1/16 and all was good. Took forever to diagnose because the noise never did centralize, it was all over the block.
     
  7. suntreemcanic

    suntreemcanic Well-Known Member

    I replaced the fuel pump. That is a great suggestion. The noise I hear travels all over the engine block. It very well could be a fuel pump.
     
  8. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Run it without the belts. A loose/cracked pulley will make all sorts of racket..
     

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