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Thread: What is the difference between 681F6015DA and 711M6015BA

  1. #1
    Bodger

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    What is the difference between 681F6015DA and 711M6015BA

    I have both blocks and they measure the same height. Not being an expert i could see no visual difference between the blocks .

    So what is the acutal difference. Can they be interchanged

    The 681F was used in the Cortina Mk2 from what i have read , and is referred to as the tall block.

    Thank you for Inputs

  2. #2
    Tyre Kicker briang's Avatar

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    Re: What is the difference between 681F6015DA and 711M6015BA

    The main external difference between the two is that the 711M is 10mm wider across the engine mounts, extra material was added to the exhaust side mounting bosses.
    Internally, the 711M has the stronger square mainbearing caps and uses cam followers with a larger stem diameter.
    681F may not have the boss for a rear dipstick hole if using a rear well sump.
    Brian.

  3. #3
    Bodger

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    Re: What is the difference between 681F6015DA and 711M6015BA

    Quote Originally Posted by briang View Post
    The main external difference between the two is that the 711M is 10mm wider across the engine mounts, extra material was added to the exhaust side mounting bosses.
    Internally, the 711M has the stronger square mainbearing caps and uses cam followers with a larger stem diameter.
    681F may not have the boss for a rear dipstick hole if using a rear well sump.
    Brian.
    Thank you Brian.

    I can see the difference pointed now that i have taken off my sunglaasses ..

    Can i used a 711 crank in this block?

    Also this block has a rear dipstick hole /boss . so most likely this was not in a Cortina ?

  4. #4
    Racer Decade Plus User wildo105e's Avatar

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    Re: What is the difference between 681F6015DA and 711M6015BA

    The 711m block is probably the best 1600 x-flow you can get excluding the ultra rare AX block. It has more material so can be bored larger etc. I am no numbers expert but is the 681 block a 1600 if so the cranks should be interchangeable. If you where to use any block it would be the 711m but the 681 may be more than adequate for what you need.

    If you use it in a earlier ford i think the dipstick will go inthe front cover (front bowl sump) just blank off the rear dipstick tube if not needed.

    to add but experts chip in I do not believe a 711m block would have been in a cortina.
    Last edited by wildo105e; 05-06-2020 at 08:17.

  5. #5
    Racer Decade Plus User Forest_rallying's Avatar

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    Re: What is the difference between 681F6015DA and 711M6015BA

    The 711m block was fitted into the MK3 Cortinas.

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