overhauling dizzy
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  1. #1
    1000+ Posts jo proffi's Avatar
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    Default overhauling dizzy

    I'm making a frankenstein dizzy housing into a cam and crank angle sensor out of all different bits and pieces , all ducciler but from a wide variety of cars.
    R20 top housing bored to fit thicker oil seal (all I could buy) , fuego? shaft, custom lid and re used thrust washers.

    This dizzy will sit on the end of the cam, attached by two slightly offset teeth that fit into the keyway at the end of the cam, and the dizzy housing and the dizzy shaft are responsible for sealing the oil in the head.

    I have two remaining areas of vaugness.

    On the engine side of the dizzy is a fibre washer. I have a few of them but first of all would like to know from an engineering point of veiw what is the purpose of the fibre, and does it need renewing or is to fit an old fibre washer acceptable??


    The second is how much endfloat should the shaft have in the housing??

    I'll be machining the dizzy housing bore to fit the new seal so am in a possition to set endfloat from scratch. I also have a stack of different thickness washers, from 0.3 -0.5 so can make up an ideal amount.

    I have read on some americam v8 sites that at temp the gap will shrink to about half if its around 0.2mm but that was probably chevy ford stuff.
    How much should I aim for on my dizzy???
    I will note that the sensors wont care how much float there is, within sensible limits (2mm or so)
    There are no points or anything moving in the housing except for a slotted cylinder and a lump of iron for the magnetic sensor.



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    Last edited by jo proffi; 17th April 2011 at 10:36 AM.

  2. #2
    1000+ Posts jo proffi's Avatar
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    Dizzy shaft endfloat ...... Anyone????





    Jo

  3. #3
    bob
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    G'day Jo,

    wouldn't reckon that the end float here would be critical, except to check that there is a little there when the assembly is nicely warmed up.

    Check how far the drive end needs to go into the head to satisfy yourself that there is a sensible gap between the drive key and the bottom of the slot in the end of the camshaft.

    Big plus over the old fug here, you can alter the static timing reasonably easily !

    cheers,
    Bob

    ps: think that there's an old r20 unit in the shed, assuming that I can find it, I could check the float on that for you if you like ?
    Last edited by bob; 18th April 2011 at 09:29 AM.

  4. #4
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by bob View Post

    ps: think that there's an old r20 unit in the shed, assuming that I can find it, I could check the float on that for you if you like ?
    That would be nice, Bob, but dont knock yourself out finding it if it is 'safe'.

    If you ever turf it on a big clean up, turf it my way so i can have a spare.

    Having the rotational ability of the r20 housing, the only tall cam mounted and slotted dizzy housing I know of gives me the option of setting the relative timing after I fabricate the unit, rather than before...with information I dont fully understand yet (setting the timing of the triggers for the ECU).


    Jo

  5. #5
    1000+ Posts PeterT's Avatar
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    Quote Originally Posted by jo proffi View Post
    (setting the timing of the triggers for the ECU).
    What's your email address? I'll send you the tool for working out the angles.

    '92 205 Mi16
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  6. #6
    bob
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    G'day Jo,

    end float is imperceptible ! However, the dog has plenty of room to move about sideways cos the hole is lots bigger than the shaft. It moves very easily so there is some float, a few thou maybe.

    Checked mr174 supplement, no mention of end float. Must be one of those things that are "met by factory manufacture & assembly tolerances". In other words, whatever feels good.

    cheers,
    Bob

  7. #7
    bob
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    G'day Jo,

    r21 is on the back of the head as well, no good as alternative ?

    cheers
    Bob

  8. #8
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by bob View Post
    G'day Jo,

    r21 is on the back of the head as well, no good as alternative ?

    cheers
    Bob
    Nope.

    Stubbie dizzies have a long oilstone bush and no secondary support. Not enough shaft length to do anything with.
    Dont let the miss's fool you..Size does matter.

    The longer shaft dizzies, ie the points style ones have a smaller oilstone baring and a secondary support a few inches up.
    This makes for a more stable shaft.

    Jo

  9. #9
    bob
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    G'day Jo,

    ahaa. OK. Always cursed that bearing when I had to play with the points....

    cheers,
    Bob

  10. #10
    Fellow Frogger!
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    Jo,

    I think you answered your own question. The Hall sensor will be "extremely" tolerant of end float. As long as the shaft doesn't sieze up, she'll be right.

    Tim

  11. #11
    1000+ Posts jo proffi's Avatar
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    Thank you tim and bob (and myself ).

    One down, one to go.

    Whats the fibre thrust washer do differently to a metal washer???



    Jo

  12. #12
    1000+ Posts schlitzaugen's Avatar
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    Not sure, but I think the fibre washer is meant to soak in some oil and expand a little bit creating a seal whilst allowing for lubrication
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