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Thread: knucklehead rocker arm noise

  1. #1

    Default knucklehead rocker arm noise

    I posted a thread last month about a company in Europe that makes knuckle rocker arms and shafts, thinking that the noise in the top end of my '47 FL was due to wear between my shafts and rocker arms. Now I'm not so sure, but would like to pick somebody's brain about this. First off, what is the clearance/ tolerance between the shafts and the arms? Second, could the noise be due to too much clearance of the rocker arm from end to end? I know there is a tolerance callout in the manual (forget right now what it is), but I was wondering if there is too much back and forth movement of the arm if it would cause a faint but noticeable knock in the top end when the motor is at operating temp. And if this is so, is there a way to take up the clearance with, say, a wavy washer placed on the shaft between the rocker arm and the mounting ear on the head? Any thoughts or help on this would be appreciated.

  2. #2
    Join Date
    Aug 2004
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    Absolutely do not put a wavy washer in there, unless you have a desire to rebuild your engine in the near future. It will fail. The standard clearance is set by the stepped thrust washer on the rocker box end. If rocker arm fit is quite loose or end play is too much the rocker shaft will slide back and forth each time the valve opens and closes. Careful shimming behind the washer or on the shaft will change the fit, however be very careful in doing so as excessive overall length affects the box to diving board fit as well.
    Robbie Knight Amca #2736

  3. #3

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    OK. thanks for the caveat and the info. Went to the manual and answered one of my questions immediately. Rocker arm/shaft clearance is .0005"-.0015". I think my noise is a combination of arm/shaft clearance and end-to-end play. Gonna see if I can make some shims out of spring steel, as I figure soft material would not be proper in this assembly. Book states .007"-.016" end to end play. Right now mine's bigger than that. My arms are also a bit over tolerance, but I'm gonna start with the inexpensive fix first. If that doesn't solve the problem, it'll be new rocker arm and shaft assembly time!

  4. #4
    Join Date
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    Be sure to shim behind the hardened washer and never against the moving part itself.
    Robbie Knight Amca #2736

  5. #5

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    Between the washer and the rocker box?

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