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Hot Rods question on bore spacing re: plymouth and chrysler flat heads

Discussion in 'The Hokey Ass Message Board' started by McAdam, May 1, 2019.

  1. McAdam
    Joined: Sep 23, 2018
    Posts: 3

    McAdam

    Hi there, I've got a bit of a project going here and I was wondering how much the flathead 4, 6 and 8s share, as far as architecture and what not. We have what I believe to be a 323 cu in flathead 8 spitfire industrial motor and my boss wants to use it in one of his hot rods. Not sure which body it is going in yet.

    Anyway, can anyone provide insight into just how much these engines shared with each other? Bore spacing is the important info here, but all info is welcome! bad ideas abound. thanks!
     
  2. Mr48chev
    Joined: Dec 28, 2007
    Posts: 24,694

    Mr48chev
    ALLIANCE MEMBER

    They have a flathead specific section on the Allpar site that will probably speed your quest up quite bit and I' think that the flathead six mopar guys on here are on there too. https://www.allpar.com/mopar/flat.html
     
  3. McAdam
    Joined: Sep 23, 2018
    Posts: 3

    McAdam

    I've read that page a few times. Information on these is scarce. That allpar page doesn't even list bore x stroke and is mainly focused on the sixes. I will continue my search online, but I thought this would be a good place to ask!
     
  4. RichFox
    Joined: Dec 3, 2006
    Posts: 9,567

    RichFox
    ALLIANCE MEMBER

    I have had experience with the flathead 4 and I doubt it shares much with the 6 or 8
     
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  5. MO54Frank
    Joined: Apr 1, 2019
    Posts: 100

    MO54Frank

    I think each division: Chrysler, Desoto, Dodge and Plymouth each had their "own" flathead 6s. I also know nothing about the straight 8. Probably be smooth with lots of torque, but not very good acceleration from stop.
     
  6. RichFox
    Joined: Dec 3, 2006
    Posts: 9,567

    RichFox
    ALLIANCE MEMBER

    upload_2019-5-1_12-56-46.jpeg Some ran OK. Digger won D/Dragster at Winter Nationals. Same guy went 250 in liner with Chrysler 8 power IMG0001_WEB-300x208.jpg
     
  7. plym_46
    Joined: Sep 8, 2005
    Posts: 3,726

    plym_46
    Member
    from central NY

    Nothing in common even between n the 23 inch Dodge and Plymouth versions and the 25 inch long Chrysler deSoto ones. The straight eights have a bit more material between the cylinder pairs. The eights crankshaft are kinda whippy and don't like rpms much north of 3500 lots of bottom end touque so you can put tall gears in a light car.
     

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