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How to determine valve closing point?

Discussion in 'Technical Q&A' started by viphoto, Dec 8, 2010.

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  1. viphoto

    viphoto Formula Junior

    Sep 11, 2010
    264
    Carlsbad, CA
    Full Name:
    Mark
    #1 viphoto, Dec 8, 2010
    So if using the theoretical, possibly "mis-translated", "use this one", "dont use that one" "replace the shim", "don't replace the shim" Black arts method of checking the opening and closing points on my 2v 308gtb I have this question.

    I choose Method #2 from an earlier Steve Magnusson post " Measure the existing clearance -- the "event" occurs when the sum of (the measured motion of the valve shim surface + the existing clearance) = 0.5 mm"

    How do you determine the closing point ... I assume you would you use the same "event arithmetic" on the other side of the lobe in reverse? Just wondering if I am on the right track. I think I can now see how the "replacing the shim to get the 0.5mm clearance" is more straight forward albeit a little more work.

    Thanks in advance
     
  2. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
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    Brian Crall
    #2 Rifledriver, Dec 8, 2010
    Last edited: Dec 8, 2010
    Replacing the shim was the proscribed method because it was felt that anyone needing to be told how to do it lacked proper tools to do it any other way. With lash set at .5mm no tool was required. Steves way requires a dial indicator. Either works quite well if done carefully.

    To measure ex closing with zero lash turn motor to the closing spec, set dial to zero. Continue turning motor until dial stops. If it shows .5mm you are done. If not advance or retard as required. If your lash is more than zero but less than .5 do the math.
     
  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
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    Steve Magnusson
    #3 Steve Magnusson, Dec 8, 2010
    Yes, for example, if the existing clearance is .008", the "opening" event occurs when you read on your dial indicator that the shim has moved .0117" down from the rest position (i.e., .008" + .0117" = .0197" = 0.5 mm); and, likewise, the "closing" event occurs when the shim is at the same elevation as the "opening" event (.0117" down from the rest postion in this example).

    Touche' -- and much easier for an Italian to say in English ;)
     
  4. viphoto

    viphoto Formula Junior

    Sep 11, 2010
    264
    Carlsbad, CA
    Full Name:
    Mark
    #4 viphoto, Dec 8, 2010
    Thanks Guys, that cleared it up for me....I appreciate your input.
     

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