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Dauntless Casting Compatibility

Discussion in 'Early CJ5 and CJ6 Tech' started by The Houston Kid, Nov 19, 2020.

  1. Nov 19, 2020
    The Houston Kid

    The Houston Kid New Member

    Houston
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    I have a ‘69 with a 991503 block casting that is locked up. As fate would have it, I was perusing FB marketplace and found a rebuilt 225 locally that is a 1254083 casting. According to info I have found elsewhere, that is actually a 231 from 1978. Does anyone know if these are compatible for the ‘69 CJ5 host?
     
  2. Nov 20, 2020
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Give us a link to your info.

    The casting numbers won't lie. A 231 will have a bigger bore, by 50 thou. Certainly the standard 225 pistons won't fit. Pretty sure that the 231 heads are different too, but that may not affect the block.
     
  3. Nov 20, 2020
    The Houston Kid

    The Houston Kid New Member

    Houston
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    Thanks for the reply. I should have stated my question more specifically: Will the 231 bolt up to existing T-14 (I think, haven’t checked model yet) and existing engine mounts, or will it require modification?
     
  4. Nov 20, 2020
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    The 225 and 231 (odd and even) will interchange physically, and some external parts (timing covers, water pumps, oil pans, etc) interchange between engines. Yes, a 231 even-fire will bolt in, but should use the even-fire flywheel.
    -Donny
     
  5. Nov 20, 2020
    The Houston Kid

    The Houston Kid New Member

    Houston
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    Great info, thank you.
     
  6. Nov 21, 2020
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Pullman, WA
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    Yep, it bolts right in using the same motor mounts and bellhousing. Here's a '77 231 odd-fire in my '68 Jeep:

    [​IMG]

    There are other small differences that are good to know about.
    • The water pump on a 231 is longer and can lead to fan/radiator clearance issues. A 225 water pump bolts on and you will need to use the 225 fan pulley to go with it.
    • The oil filter is angled differently on the 231 and can rub against the lower radiator hose in a Jeep.
    • The 231 uses a large bore Rochester 2G carburetor versus the small bore 2G on the 225. This means you can't swap carbs without swapping the intake manifold.
    • The 231 will come from the factory with an HEI electronic distributor which is nice.
    • As Donny said, the '78 231 is an even fire and will need an even fire flywheel for proper balance.
     
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  7. Nov 24, 2020
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
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    Take note - the timing marks on the 225 to 231 can be 18* different and WILL cause timing issues. You can have a 'neutral' balance put on the 225 fly wheel and it will work fine in a 231 EF.
     
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