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Maximum RPM of flatheads?

Discussion in 'The Hokey Ass Message Board' started by perrysmith, Jun 15, 2013.

  1. perrysmith
    Joined: Jul 6, 2008
    Posts: 257

    from Idaho, USA

    Anyone know what the peak RPM of a flathead is, in general. Also, the top RPM of a built-up one? Reason I am curious is that I have a 6 V SW tach and wonder if the top reading of 4500 pulls in all the flatheads. Thanks in advance.
  2. daddio211
    Joined: Aug 26, 2008
    Posts: 5,999


    A stock flatty will see a few trips to 4000+ before becoming terminally ill.

    A race engine is a whole 'nother story though. If I remember correctly the Poteet & Main Flat Fire's flatty was wringing out 10,500.

    Sent using the NEW Droid HAMB app from atop my toilet.
  3. OldColt
    Joined: Apr 7, 2013
    Posts: 504


    A friend of mine had a stock V8 flathead in a '51 Ford. The motor was low mileage (around 20K as I remember). When he ran it hard though the gears with a 3 speed manual the motor seemed to peak around 3500 rpm on the tach, and he shifted at 4000 rpm. Hope that helps some. --- Steve ---
  4. The factory hp ratings were at 3800 for a stocker. I know of two with stock bore and stroke but blueprinted, full pressure, and many racing tricks that turn 6-7000.

  5. 1934coupe
    Joined: Feb 22, 2007
    Posts: 4,429



  6. T&A Flathead
    Joined: Apr 28, 2007
    Posts: 1,850

    T&A Flathead

    When Im driving mine hard, I shift at 5500rpm. A well built engine will stay together and still pull.
  7. 4dFord/SC
    Joined: Sep 12, 2004
    Posts: 837


    I have a 5k Sun Football tach on my warmed up '40, but don't think it's ever pulled more than 3500. Your 4500 SW should be fine.
  8. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    from Texas

  9. PackardV8
    Joined: Jun 7, 2007
    Posts: 890


    The flatmotor will rev a lot of RPMs unloaded in neutral, but it runs out of breath early on under load. It takes much port, block and head work to make any horsepower above 4,500 RPMs.

    jack vines
  10. 3wLarry
    Joined: Mar 11, 2005
    Posts: 12,804

    Member Emeritus
    from Owasso, Ok

    Our flathead powered Hamb Dragster would turn 6000rpm's in the lights on a regular basis.
    kidcampbell71 likes this.
  11. Ice man
    Joined: Mar 12, 2008
    Posts: 982

    Ice man

    I remember yrs back a Hot Rod Mag article on a Flatty that was reverse flowed, and he was running at the Salt Flats. The tranny stuck in low and he ran it anyway, and it hit 10000 + RPM. Don't remember to much more as it was many yrs ago. Iceman

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