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Thread: Need help with the flat head in my truck

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  1. #1
    paul71 is offline Registered User Visit my Photo Gallery
    Join Date
    May 2001
    Kansas City, Missouri
    Car Year, Make, Model: 1948 Dodge Pickup

    I want to see if I can get the Flat-Head straight 6 in my truck running. What do I need to check? or Is it basically like every other engine out there? I never dealt with a car or truck this old before. It also has a fluid drive trans in it. How do I check to see if its good and, if it is good, get it working? It ran when it was parked, so if I can get it running. I might see if I can get it street legal and drive it, while I finish my 'Cuda.
    1971 Plymouth 'Cuda
    1948 Dodge Pickup

  2. #2
    Larry M's Avatar
    Larry M is offline Senior Club Hot Rod Member Lifetime Contributor Visit my Photo Gallery
    Join Date
    Apr 2001
    Car Year, Make, Model: '23 Tall "T" Coupe 400 SBC

    Originally posted by paul71
    I want to see if I can get the Flat-Head straight 6 in my truck running. What do I need to check?

    I had an old V8 Flatty with an Offy Tri Power setup in a 50 Ford years ago. When I bought the car($50) I tore the Offy(aluminum)heads off and found some small cracks between the exhaust and intake valve seats. Also the heads were warped a bit but I was able to have them shaved enough to be in spec. Money was scarce back then so I had the cracks between the valve seats welded by a friend, the thing ran great after that.

    Those are at least two things I would check, also check the space between the cylinders for small cracks. I would do some other things like dropping the oil pan and check it out (missing little engine parts in it).
    Sorry, not too sure on the (slush box??)tranny tho.

    Good luck with your project.


  3. #3
    Jerry Rowley is offline Registered User Visit my Photo Gallery
    Join Date
    Jan 2002

    Paul the biggest item is, does it turn over? If it's not frozen then like all engines, it needs compression, fuel and spark and it will run. Many old flat heads had a common problem of stuck valves (stuck open). You can find out by giving it a compression test. If you can turn it by the starter, pull the plugs, put some Marvel Mystery oil in each cylinder (or WD40) and then use a standard compr. tester. Next, find out if you can get a spark with the hot coil lead to ground. After that, replace the fuel with new, add a little alcohol to the tank to take care of any water. Then see if you can get fuel to the carb. Spray the carb liberally with carb cleaner. Next try a little ethyr spray and crank it. If it pops, it will eventually run!

    If it runs, then put tranny fluid in that fluid drive and pray! it might still work OK, but the seals are going to leak like a sive. If it will move at all, try some tranny stop leak and drive it about 100 miles.

    Good luck! I haven't played with one of those since my 1950 Dodge car!


  4. #4
    southerner's Avatar
    southerner is offline CHR Member/Contributor Visit my Photo Gallery
    Join Date
    Jun 2004
    Car Year, Make, Model: 69 Holden HT

    Been years since I played with the old flatties. The one good thing about em is it,s impossible to drop a valve in them.

    Seriousely though those old moters were bulletproof and had heaps of low down torque. Looked after properly they will probably go forever.
    "aerodynamics are for people who cant build engines"

    Enzo Ferrari

  5. #5
    suedeplymouth's Avatar
    suedeplymouth is offline CHR Member Visit my Photo Gallery
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    Dec 2003
    Car Year, Make, Model: '64 ranchero

    Since im fairly familliar with mopar flat 6 bangers, ill tell you what I know. Mine has tons of bottom end torque and thats it, theyre slower than dirt. Theyre darn near indestructable, even if they are stuck you could get it unstuck. Those old semi-autos werent bad, ive seen several resurected from the boneyard and work fine after they were played with.
    "its better to rule in hell, than serve in heaven."

  6. #6
    The F.N.G.'s Avatar
    The F.N.G. is offline CHR Member Visit my Photo Gallery
    Join Date
    Sep 2003

    I would suggest that before you try to turn it over pour some wd-40 in the cylinders until it almost reaches the spark plug holes. Let it set for a week or so and then try turning the engine over by hand with the sprark plugs out. If it turns over freely then you're almost home free. When turning it don't turn it more than acouple of revolutions just in case it is a pressure fed engine-you don't want the oil pump trying to pick up the sludge that's in the oil pan now.

    Report back on whether it turns over or not.

    Technology is the answer.

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