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Is my 8BA Flathead Crankshaft f*cked (endplay)

Discussion in 'The Hokey Ass Message Board' started by Deadelvis2000, Feb 7, 2012.

  1. Deadelvis2000
    Joined: Feb 10, 2007
    Posts: 173

    Deadelvis2000
    Member
    from Austin, TX

    Fellas,

    I have been taking apart a 52 8BA Flathead. It seemed to be in very good shape. Oil was clean with very little sludge in the pan and lifter gallery but had excessive crankshaft endplay. You could tug on the crank and it would move alot. Alot meaning it seemed to move 1/16th". Now when I removed the oil pan and rear main cap, I noticed that there has been some trouble. As you can see...the rear of the bearing has been damaged and some of it has chipped away. The rear trust surface (cap bearing) is also heavily scarred. The thin rear crank thrust surface is grooved and appears thin. Now here is where I find if I am in trouble.

    I miked the distance between the crank thrust surfaces at around 2.371
    and when I mike the outer edges of the cap bearing I get around 2.340
    and in some places 2.325!!!

    Does anyone know what a stock rear main bearing width is??? Has my crank been destroyed??
     

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  2. gerry miller
    Joined: Feb 3, 2012
    Posts: 108

    gerry miller
    Member

    I would guess the crank is good. Thrust bearing takes up pressure from clutch being pushed in and usually wears out first.Somebody out here knows the dimension for sure.
     
  3. 64gal
    Joined: Jan 18, 2007
    Posts: 133

    64gal
    Member

    I just measured the crank and the thrust bearing on my broken 8ba and I got 2.25 with a caliper, also I couldnt get a good read on the crank because of the counterweights. I checked in a flathead book and it says "main bearing journel length,rear 2.255" mainbearing length rear2.251 and wall thickness is.0855 Sounds like you should have .004 clearence. I think a good crank grinder should be able to help you. Hope this helps and goodluck, Tom.
     
  4. 64gal
    Joined: Jan 18, 2007
    Posts: 133

    64gal
    Member

    I also ment to say a good crank grinder that can weld and restore the thrust surface.Your journal width is too wide. Tom.
     
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  5. Deadelvis2000
    Joined: Feb 10, 2007
    Posts: 173

    Deadelvis2000
    Member
    from Austin, TX

    Thanks Tom.

    In my haste, I read the mic wrong. It was 2.271 overall length which would make the crankshaft thrust fin worn down approx .020. I will have to have the crank restored as you say. Thanks for the prompt information. I feel a little better knowing that it can be remedied.
     
  6. flatjack
    Joined: Feb 13, 2007
    Posts: 600

    flatjack
    ALLIANCE MEMBER

    I would look for a different crank. 8BA cranks should be available cheap. I've got a bunch of them, but I'm in Wisconsin.
     
  7. mastergun1980
    Joined: Oct 18, 2010
    Posts: 1,062

    mastergun1980
    ALLIANCE MEMBER
    from Alva OK

    Ok while It wasn't a flathead crank , I had a 289 crank wear in this manner. ( in fact the thrust bearing ate into the crank) Do yourself a favor and find another crank- Flatheads are expensive to rebuild so take the nessairy precautions!
     
  8. That comes from dum'asses holding the clutch in at stop lights and such, maybe a truck with a lot of miles and shifting ,,,,,,
     
  9. Deadelvis2000
    Joined: Feb 10, 2007
    Posts: 173

    Deadelvis2000
    Member
    from Austin, TX

    Yep...It came out of a big truck so I imagine that it was heavily used. It has been rebuilt at one time or another as the rod caps are stamped and the pistons are 060 over. I wonder if they didnt clean out the sludge in the crank oil passages before they reinstalled. It definately seems like a f*ck up because besides that the motor is
    in surprisingly excellent condition.

    Anyone near Austin have an extra 8ba crank?????
     
  10. Deadelvis2000
    Joined: Feb 10, 2007
    Posts: 173

    Deadelvis2000
    Member
    from Austin, TX

    Has this happened to anyone else's flathead?
     

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