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Technical Chevy auto behind a Flathead

Discussion in 'Traditional Hot Rods' started by Idaho/Dave, May 27, 2020.

  1. Idaho/Dave
    Joined: Jul 22, 2007
    Posts: 531

    Idaho/Dave
    Member
    from Idaho

    A friend ask if anyone makes a adaptor for a chey 350 auto to a flathead.
     
  2. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 5,529

    Ebbsspeed
    ALLIANCE MEMBER

    Country Joe likes this.
  3. mkubacak
    Joined: Jun 20, 2005
    Posts: 199

    mkubacak
    Member

    Nope. Manual transmissions only. Gotta have that third pedal in there for more fun.
     
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  4. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,047

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    I am a high achiever I guess....I mastered driving a manual shift (first) and then went on to further success learning how to handle an automatic like a pro. ;)

    I think it is called being ‘ambipedaldexterous’

    Ray
     

  5. Kiwi 4d
    Joined: Sep 16, 2006
    Posts: 3,095

    Kiwi 4d
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  6. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,047

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    IMO , the most efficient automatic would be a Ford C-4. And efficiency would be a primary consideration with the typically anemic flathead Ford.:D
     
  7. Marty Strode
    Joined: Apr 28, 2011
    Posts: 5,937

    Marty Strode
    Member

    And the Flat-O-Matic, conversion is high quality, and available in nearby Salem, Oregon.
     
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  8. solidaxle
    Joined: Jan 6, 2011
    Posts: 548

    solidaxle
    Member
    from Upstate,NY

    I think it is called being ‘ambipedaldexterous’[​IMG]
     
  9. adam401
    Joined: Dec 27, 2007
    Posts: 2,456

    adam401
    ALLIANCE MEMBER

    I've never driven a flathead with an auto behind it. I would think it would be a total dog. I love flatheads and have one in my car. Im Also not trying to say anyrhing negative about automatics because I know some people have a need for one. Im just curious if anyone has driven that combo and what it was like.
     
  10. wheeltramp brian
    Joined: Jun 11, 2010
    Posts: 1,168

    wheeltramp brian
    Member

    I built a 33 coupe for a customer.stock 8cm and c4,quickchange with 3.70 final ratio and 30 inch rear tires.was a gutless wonder.id never doit again.same customer I built a 29 roadster on 32 rails,stock 8ba,39 trans ,same gears and tires.the thing was peppy and great
     
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  11. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,047

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    That seems really odd. The stock ‘51/‘53 factory flatheads with FOM/MOM, while no ball of fire, but were decent everyday drivers and they likely outweigh the ‘33 Coupe by at least a few hundred pounds and had 3.30ish gears, IIRC.

    Further, years ago I bought my wife a ‘65 Falcon, and I also had ‘64 Falcon, both stock six w/C-4 and they too, drove decently, not hot rods, but quite adequate for dailies.

    When something doesn’t seem quite right, it usually isn’t. Maybe expectations were too high, maybe a trans problem? :confused:

    Ray
     
    Last edited: May 28, 2020
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  12. oldsman41
    Joined: Jun 25, 2010
    Posts: 1,362

    oldsman41
    Member

    Just asking, would the Ford od trans work I’m running the 3 sod manual with od now and the rear gear is 4.27 wife loves the car but can’t drive a stick.
     
  13. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,047

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    The Ford AOD for small block Ford’s is same block bolt pattern as the ‘65 up C-4. The thing you will have to be careful of is the flex plate you use. Fords have two tooth counts, 157 and 164. In addition, SBF are externally balanced, early models have a 28 oz weight, around 1980 or so they went to 50 oz.

    Some years ago I put an AOD behind a ‘67 289 and got an aftermarket flex plate with the correct combination of tooth count and weight.

    For your Flathead, which is internally balanced, I believe you would want an unweighted 157 tooth flex plate with the correct converter bolt pattern. I think the converter pattern is the same as a C-4, but I can’t recall for certain. If they are the same, the flex plate that comes with the C-4 adapter should be just what you need. I am sure the adapter dealer can guide you.

    Ray
     
    Last edited: May 28, 2020
  14. oldsman41
    Joined: Jun 25, 2010
    Posts: 1,362

    oldsman41
    Member

    Thanks hnstray
     
  15. My avatar 39 Ford is flathead powered with a C-4 shift-kitted auto, installed using Flat-O-Matic adaptor kit............an 8" Ford rear end with 3:55's..............everything bolted up like it was factory made.........pulls 2350 rpm @ 65 mph........
     
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  16. flatford39
    Joined: Dec 3, 2006
    Posts: 2,800

    flatford39
    Member

    That's interesting info right there. Might make me reconsider what I am doing with one of my projects.
     
  17. oldsman41
    Joined: Jun 25, 2010
    Posts: 1,362

    oldsman41
    Member

    Yeah I will probably stay with the 4.27 gear cause it’s a 51 merc kinda heavy. It’s got me thinking, I have a ford auto od and a 302 motor but I love that flatty.
     
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  18. Garpo
    Joined: Jul 16, 2016
    Posts: 231

    Garpo

    Have done a couple of conversions. first was a Powerglide from an Aussie Holden six. Worked well in my '32 sedan for normal driving, certainly kept up with the traffic OK. Downfall was hill country. Would hold lo gear up hill, and rev as hard as I wanted to push it, but I really wanted a middle gear. I drove it like that for 10 years.
    My solution was a Toyota 4 speed auto ex Supra etc. with overdrive top. Used a bell housing kit from Flatattack. Love the set up. 3.9 rear gear gets off the line well, and cruses at 2000rpm @ 60mph.
     
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  19. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,047

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    @Garpo ......does that automatic require any additional controller for OD or torque converter function?

    Ray
     
  20. 40FORDPU
    Joined: Mar 15, 2009
    Posts: 3,100

    40FORDPU
    ALLIANCE MEMBER
    from Yelm, Wa
    1. Northwest HAMBers

    I ran a C4 a/t (Flat-O-Matic kit) behind a flathead in my '40 p/u..worked well.
    Engine was an 8ba, bored .080, balanced, Edelbrock heads, Fenton dual carb intake, cast iron headers, MSD dist-MSD 6 box, trans had a shift kit, 3.00 gears.
     
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  21. I can't speak for all Toyota 4 speeds, but the ones I have put behind flatheads do not in a computer/electronic sense. They have a button on the stock shifter handle to go to overdrive. I assume there's a solenoid in the transmission. You could mount the button anywhere, just a couple of wires.

    I have also used the Flatattack adaptor, very easy.
     
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  22. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,047

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    @X38 Thank for that info. A couple more questions arise. Is the torque converter a lock up unit or not? And, am I correct inferring the Flat attack adapter replicates the early Ford V8 transmission bellhousing shape and bolt pattern. Lastly, how much does it sell for in AUS $ ?

    Ray
     
  23. Here it is on the website:
    https://flatattackracing.com/
    That would be $400USD.
    You need the Ford hogshead to go with the adaptor for late engines.

    He also makes kits for multiple transmissions, manual and auto.
    Going by the website there are 3 North American distributors.

    Lockup? From memory I don't think so.
     
    Last edited: May 29, 2020
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  24. sloppy jalopies
    Joined: Jun 29, 2015
    Posts: 4,778

    sloppy jalopies
    Member

    I had blaine at Lewiston tranny take up the bands in a C4 for me...
    that little 268 would chirp second gear rubber at will..
    I ran them for awhile... broke the flexplates…
    the center of the flathead crankshaft is not centered in the bell housing's bolt circle.... flato flexos were $140 something, bought 2... then I … sorry... dropped the 302 back in front of the AOD.
     
  25. Garpo
    Joined: Jul 16, 2016
    Posts: 231

    Garpo

    Early versions are straight forward conventional auto with a switch / solenoid to lock out the overdrive. Later models linked to the computer and involved more things to stay away from. Some models have torque converter lock up.
    There was a version of this Aisin trans used in rear drive Volvos which may be worth investigating.
    When I was looking into this swap, I found lots of info on the 'net. Hardest part was to sort what was relevant to the project without getting out of hand with technology.
    I built my own shifter using an early Ford gear lever, so there is no immediate evidence if someone looked inside..
    If using an o/d trans keep the rear end gearing in mind - target your highway cruising speed rpm to suit your engine set up. Usually 2000 - 2400 rpm. with a 4-1 or similar gear. Back to high school maths, tire diameters etc.
     
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  26. Mr48chev
    Joined: Dec 28, 2007
    Posts: 29,546

    Mr48chev
    ALLIANCE MEMBER

    Well this thread proves one thing, NEVER FRICKING ASSUME UNTIL YOU SEARCH THE FACTS.
    Especially if you type slow.
    Different folks have entirely different reasons for running an automatic but there are guys on here who I swear would tell a guy with no left leg to grow another one so he could push a clutch pedal just to please them.
    Wife that can't handle a stick and is not about to learn is probably the second best reason outside of your left leg not being able to push a clutch pedal if you still have a left leg. Yea we know it is going to be a bit of a slug but I haven't seen a lot of flathead 49/51 Mercs doing any serous drag racing lately.
    Trans wise I think I'd use a 200R4 rather than a 350. That extra gear evens things a bit on the longer roads.
     
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  27. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,047

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    @Garpo ......Thank you for the reply and information. I appreciate it.

    Ray
     

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