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2F Knocking noise at idle?

Discussion in '40- & 55-Series Tech' started by 78crzr, Feb 22, 2004.

  1. 78crzr

    78crzr

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    Well, took the 40 out today for the first time since the carb. rebuild. I'm getting a knocking noise while idling. The engine supposedly has 107,000 miles, but for all I know it could be 207,000. The title was mileage exempt. I've owned it for about a year and put 3,000 miles +/- on it and never heard the knocking sound before. Any ideas what it might be?

    I'm also noticing some smoke upon taking off from stops. Didn't notice this before the Jim C. carb rebuild, although I'm very doubtful the carb has anything to so with the smoke. I'm wondering if it is head rebuild time, or total engine overhaul time? :eek:
     
  2. Poser

    Poser Oh...Durka Durka Durka. s-Moderator Supporting Vendor

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    Does it speed up and get louder with an increase in the engine RPM's?
     
  3. 78crzr

    78crzr

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    Can't really hear it at anything more than idle. Guess I need to pop the hood while idling and bip the throttle and see. Any ideas either way?
     
  4. Poser

    Poser Oh...Durka Durka Durka. s-Moderator Supporting Vendor

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    Well, if it does not increase intensity with engine RPM's, and you have strong oil pressure, I would not worry about it, as I have known a few 2F's that have had a low 'knock' sound at idle, and ran for years, and are still going, without any problems...But generally speaking, a steady knocking from the engine is not a good thing...You could have a rod bearing that is starting to lay down on you, but without dropping the oil pan, and dropping the rod bearings, you will not know if it is something in the bottom end, of course, unless it lets go while running, in which case, you will know EXACTLY what it was...

    Good luck!

    -Steve
     
  5. Eternal

    Eternal

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    Mine has knocked constantly since I got it 12 years ago. Never had a problem with it. It seems to scare most people but hasn't bothered me. (though I am still swapping for a 4.3)
     
  6. rgentry

    rgentry

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    Get a 4 foot long dowel and put it against various parts of the engine while it is running (don't stick it in the fan blades!). Put the other end of the dowel up to your ear and you will hear the knock. This is a poor man's stethoscope.

    I have a similar knock and have identified it as coming from the timing gears. With the dowel method, you can (sortof) tell whether an engine noise is coming from the top end or bottom end and approximately where along the length of the engine. Push the clutch end and see if the noise changes as some tapping, knocking noises can come from the clutch.
     
  7. Quazii

    Quazii

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    I had a similiar knock from my F. After dropping the oil pan I found it was just a loose weld on one of the baffles in the pan. The baffle was just tapping the oil pump strainer. Not sure of all the lower end differences from the F to the 2F but it might be a similiar gremlin
     
  8. PabloCruise

    PabloCruise

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    My 2F has "purred" ever since being rebuilt (~20k ago).

    Make sure your valve lash is set, oil pressure is good and then enjoy it...
     
  9. 65swb45

    65swb45 Supporting Vendor

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    my first thought was a loose rocker-pushrod. After reading the other posts, I also remembered the swb has a knock in the timing gears. Been there for 8+ years now, ever since I took out the grenaded fibre cam gear and put a steel one in! Too lazy to put a matched new set in.

    Ditto on the dowel stethescope suggestion.
     
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