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Flathead 8ba

Discussion in 'The Hokey Ass Message Board' started by keith27T, Jul 3, 2013.

  1. I found a couple of 8ba blocks and had them both thermo cleaned and checked for cracks. 1 has a crack from the valve to a cylinder which has been sleeved. Junk ? The other is okay but will probably need new valve seats and probably 2 sleeves because 2 cylinders have pitted. Should I fix this one, or look for a good one. Kinda getting tired of looking, and taking things apart and hauling things around. What would you expect to pay for a good clean crack free block?
  2. JohnEvans
    Joined: Apr 13, 2008
    Posts: 4,883

    from Phoenix AZ

    If the cracked one is a exhaust valve ,scrap as that would be a $$$ fix. How deep are the pits ,will a .120 over bore clean them up. Pistons for that size are readly available and you get a usuable displacement increase. Good block $300-400 UPPPPP!
  3. Picking up blocks in the morning. Let you know . How do I tell if it is the exhaust valve?
  4. If I remember correctly, it E-I-I-E-E-I-I-E, front to back on either side.

  5. Thanks. RB35. I'll check it out.
  6. 296 V8
    Joined: Sep 17, 2003
    Posts: 4,666

    296 V8
    from Nor~Cal

    Considering they can be bored 120 + over … the pits probably aren’t an issue.
    Save the cracked one … it will be worth fixing someday.
  7. tubman
    Joined: May 16, 2007
    Posts: 5,587


    A lot of them will go 3/16" (.1875) over. Make sure you have it sonic checked. As I mentioned in a post a couple of weeks ago, Speedway seems to be liquidating their flathead pistons. They listed a set of 3 3/8 stock stroke pistons for less than $200. That's a lot of pit removal room. Back in the day, some guys were able to overbore a 3 3/8 engine .010 to re-ring it. I don't know if I would stand behind that.:rolleyes:
  8. I'll check the bore size I think that block was .010 or .020 over.
    Last edited: Jul 3, 2013
  9. 55willys
    Joined: Dec 7, 2012
    Posts: 1,615


    A friend rebuilt one without having it sonic checked turns out it was core shifted. Blew out the side of the cylinder wall where it was only about 1/16 thick. Jim (55willys)

  10. eeks not nice!
  11. Dale Fairfax
    Joined: Jan 10, 2006
    Posts: 2,585

    Dale Fairfax
    Member Emeritus

    Sounds like mine: it's an 8BA that had been bored to 3 3/8 long ago. Broken rings dictated a cleanup-the machinist found +.030 pistons for 3 3/8 so bored the block .030 over. Two cylinders "found water" which meant I'd been running with approximately .015 of wall thickness. The holes were down low in the bore so probably never exposed to cylinder pressure. We sleeved the entire block (it already had 2 due to previous problems.).

    Never scrap a Flathead block unless the center main web is ready to fall out of it. Most things that can be seen on the top side can be repaired. Pinning, sleeving, and, as a last resort, welding, can save about anything.

  12. Picked up the blocks the one with the pitted cylinders is pretty bad. I think it would be a better idea to sleeve them. Don't want to bore them, to risky. The other is cracked at least at 2 exhaust valve and a couple of intakes, but the cylinders are nice. They said it could be fixed, but would have to be shipped to the states and get welded there and pressure test. Costly!
  13. tubman
    Joined: May 16, 2007
    Posts: 5,587


    3 3/8 +.030 ?! Even I wouldn't try that! That said, I have heard some have cleaned up at .010.
  14. Bearing Burner
    Joined: Mar 2, 2009
    Posts: 912

    Bearing Burner
    from W. MA

    I had a 3 3/8 +.030 engine cracked it after a couple of runs still have 8 pistons after 40 years.
  15. Well my machinist is away this weekend racing. So I won't be able to get the block to him till next weekend. I'll keep you guys posted.
  16. Pete1
    Joined: Aug 23, 2004
    Posts: 1,953

    from Wa.

    I had one that was 3 7/16 + .020 with .090 wall left.
    Since 1952 I have built or machined 10 flatheads with 3 7/16 bore.
    Of those 10 engines it took over 100 blocks to find 10 that would end up with .090 walls.
  17. F91
    Joined: Dec 29, 2012
    Posts: 126


    Keith, seems like there are several running flatheads available in the Seattle area....
    Last edited: Jul 5, 2013
  18. PackardV8
    Joined: Jun 7, 2007
    Posts: 890


    Good luck finding one that isn't cracked a bit somewhere. Can't remember the last one which was perfect.

    jack vines
  19. tubman
    Joined: May 16, 2007
    Posts: 5,587


    Your last sentence says it all.
    Last edited: Jul 6, 2013
  20. Well took the block to the machinist. He's going to measure the bores and bore and sleeve most likely three cylinders, to the minium. New valve seats and the block should be good to go.
    Have another question. I have a mercury 4" crank, but not from this block. He said it might be a problem to use the crank, because the longer strock will hit the block, so he would have some grinding on the block to make it work. He suggested using a regular crank. The block I got the crank out of was a C 8BA block #and the block we're working on is also a C 8BA block#. Has anybody run across this problem before?
  21. Vergil
    Joined: Dec 10, 2005
    Posts: 785


    The crank will fit just fine with no machining, the mercury block is the same as the ford. Go with the mercury crank, ford and mercury use the same connecting rods.
  22. tubman
    Joined: May 16, 2007
    Posts: 5,587


    I think you need another machinist. I have never heard of anyone having a problem putting a stock 4" Merc crank in an 8BA. If thsi guy is telling you this, run as fast as you can and find somebody else.

    Everything this guy has told you is now suspect.
    Last edited: Jul 13, 2013
  23. Nah, I don't think so, the guys bin building engines for years.
    He's built for me to, very compitent builder with a list of references a mile long. Maybe its been awhile since he's done a flathead. Mostly builds engines for drag racing. Good guy.
  24. Pete1
    Joined: Aug 23, 2004
    Posts: 1,953

    from Wa.

    Did your machinist want you to leave your 4 inch crank with him so he could dispose of it safely for you??
    He may know a lot but you haven't led us to believe that.
  25. Who's doing your machining?
  26. model.A.keith
    Joined: Mar 19, 2007
    Posts: 6,279


    4'' crank in an 8BA ..should all fit with no problems...........:D


  27. No I have to get the crank magged and ground yet.

    I don't know maybe I got it wrong. Anyway glad it will work.
    Thanks for the input.

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