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Technical Info on Thickstun PM7 flathead manifold

Discussion in 'The Hokey Ass Message Board' started by dirty old man, Nov 20, 2016.

  1. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,912

    dirty old man
    Member Emeritus

    My club brother Tudor bought an A/V8 tub a couple weeks ago, and while it's basically a solid car, there are a few bugs, including a very sluggish engine.
    59A flathead, only visible modification is Thickstun intake with 94 carbs, one of which is blocked off with a plate between carb and manifold. Manifold has cast in number "PM7".
    There is a bit of doubt about whether this manufold is a conventional 180 degree with only small balance passages between front and rear carbs, or a 360 degree common chamber feeding all 8 cylinders. I'm thinking it's a 180* and another old fart like me is thinking 360*o_O
    Obviously if it's 360* it will run OK on 1 carb, just not breathe as well as it would with 2. But if it's a 180* and you're trying to run it with one carb blocked off, there's gonna be 4 cylinders only getting what air/fuel mixture that can get thru the balance passages, which ain't much:confused:
    I haven't been inside a flathead in about 50 years, and the only Thickstun manifolds I ever saw were in magazine pics, and I don't recall seeing a pic of the Thickstun's underside, which would reveal whether it's 360* or 180*. Anybody out there that knows from personal experience whether it's 360* or 180*, please respond.
     
    Dog_Patch and Tudor like this.
  2. Petejoe
    Joined: Nov 27, 2002
    Posts: 11,227

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    [​IMG]

    These are great intakes. Adds Horsepower.
    You shouldn't have any issue running both carbs.
    I'd definitely unblock the other inlet.
    You are starving four cylinders.
     
    Tudor likes this.
  3. Petejoe
    Joined: Nov 27, 2002
    Posts: 11,227

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

  4. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,912

    dirty old man
    Member Emeritus

    Petejoe, it appears you are showing 2 different manifolds, the first obviously a 180*, and although the second is different and sorta flat on the bottom, it also appears to be 180*.
    But are both PM7?
     
    Tudor likes this.

  5. Petejoe
    Joined: Nov 27, 2002
    Posts: 11,227

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    These were taken from google. I'd bet money the differences are between the old ones and the repops.
     
    Tudor likes this.
  6. Thank men! Any commentary on what jets you would need with two carbs? The motor is supposed to be bone stock and bot built. I was told the theory is two carbs were just too much. So I guess the question is can we do the two carbs?

    It starts really nicely and runs/drives well and it starts to skip and break up a bit when you try to let her pull to wind first or second. Ive ridden in Laydrags Merc and it is nowhere near that peppy but his engine is stroked and built
     
    Last edited: Nov 20, 2016

  7. Hey Petejoe! Longtime! Finally ended up with a flathead. I guess this long on the hamb and one of these will have to get on you It is cool as hell. Love it.
     
  8. Petejoe
    Joined: Nov 27, 2002
    Posts: 11,227

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    Hi Tudor!
    Yes they grow on you. After a while going fast isn't as cool as the sound and looks of a flatty.
    Ran dual carbs on a stock 21 bolt years ago. Yes it makes them more spunky.
    There are volumes written here with your question.
    Lots to learn. Read read.

    [​IMG]
     
    Dog_Patch likes this.
  9. Petejoe
    Joined: Nov 27, 2002
    Posts: 11,227

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

  10. That's a cool write up. Good ol edelbrock slingshot sure looks good and out performs. I need one of those.
     
  11. Spoke with Flathead Jack today. What a great guy. I appreciate the guys that take the time to answer some questions. Reading everything I can. Lots of good information out there. Sure is cool when a guy with experience takes the time to help the newbies. Making small improvements all the time and really digging the A V8.
     
  12. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,912

    dirty old man
    Member Emeritus

    And what did Flathead Jack say about the manifold, 360* or 180*?
     
  13. thirtytwo
    Joined: Dec 19, 2003
    Posts: 2,641

    thirtytwo
    Member

    The "average horsepower number" for 2000-3400 was very little differance for all the intakes , I heard long ago that all the tall intakes were better street intakes and the low were better for high rpm , not to many people going to be constantly spinning a flathead 5000 rpm these days
     

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