Axial space between crankshaft and leading main bearing

Discussion in '1947-1954' started by wokri, Apr 8, 2017.

  1. wokri

    wokri Member

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    It seems that the crankshaft of my engine 235 cui has to much space in axial direction between the leading main bearing and the crankshaft. How large may max. the space?
    Ask
    Wolfgang
     
  2. coilover

    coilover Member

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    Pry the crank all the way forward and then all the way back; there should be from 0.003 inch to 0.009 inch clearance at the thrust bearing as checked with a feeler gauge. You probably need to check my math but I believe that is from .076mm to 0.23mm.
     
  3. wokri

    wokri Member

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    Ok, thank you for your answer.
    If my engine garage will told my right, than have the crankshaft 0,5mm/0,019685 inch space. That's too much? If this messure will right, what can I do?
     
  4. Bill Hanlon

    Bill Hanlon Member

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    Like Evan says, the measurement is taken at the thrust bearing, NOT at the "leading bearing". I take "leading bearing" to mean the front most. I don't remember if the thrust bearing is the 2nd or 3rd from the front.
     
  5. coilover

    coilover Member

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    Almost twenty thousandths of an inch is too much. Do you have an automotive machine shop that can weld thrust surfaces and grind back to spec? I just had a 406 Ford crank done in this manner and it looks good but it always causes some warping. Good shops straighten the crank close enough that a 0.010 grind will put it right on spec. On an old Chevy truck with just a regular pressure plate wear on the crankshaft thrust surface is nearly always caused by keeping the clutch pedal down for extended periods of time. Shift into neutral if the stop is longer than 30 seconds.
     
  6. wokri

    wokri Member

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    I had a idea, i took a second thrust bearing and put into the first bearing cup, mill one side down and size the other side down, so that the axial space will get smaller. What do you think?
    Answer me.
    Wolfgang
     
  7. Bill Hanlon

    Bill Hanlon Member

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    I like the traditional way (as Evan says) a lot better. You would not just need to modify the bearing, you would also have to grind a flat surface on the first front of the first crank throw big enough to provide the necessary surface to contact the modified bearing.
     
  8. wokri

    wokri Member

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  9. Bill Hanlon

    Bill Hanlon Member

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    .001" undersize bearings are designed to be used with a standard (uncut) crankshaft with a little wear, but otherwise in good shape. The bearing in the picture is used, so my question would be "What condition is the crankshaft in?"

    I've seen main bearings in undersizes of 0.001", 0.002", 0.010", 0.020" and 0.030"
     
  10. wokri

    wokri Member

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    Here is a pic of the crankshaft:
    Kurbelwelle
    Tell me what do you think!
     
  11. Bill Hanlon

    Bill Hanlon Member

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    Looks like an engine to me.
     
  12. wokri

    wokri Member

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    Ok, Bill. You think, that I should buy this engine?
     
  13. Bill Hanlon

    Bill Hanlon Member

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    Sorry, but not near enough information for me. Overhaul it before use? I'd need to get inside it with a micrometer and some PlastiGauge before deciding if I could use it as is.

    Just curious if the wear allowing the axial movement if in the bearing, the crankshaft or both. I don't have specs for Chevy 235, but I'll bet someone on this forum has them.
     
  14. wokri

    wokri Member

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    Hello,
    I've bought the crankshaft. The crankshaft cost 250 €. The main bearings were standard bearings, I think I'll grind the crankshaft up to the first under size .010
    Wolfgang
     

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