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Technical Flatattack (8BA) style heads on a 99A Mercury?

Discussion in 'Traditional Hot Rods' started by 1933phaeton, Jun 13, 2018.

  1. I have a set of Flatattack 8BA style heads (with water outlets at the front) in VGC and I was wondering whether these can be fitted to a 99A Mercury engine. I am aware the early 24 stud heads can be fitted to an 8BA with a few changes. Can the same be done with the 8BA heads to an earlier 24 stud engine. Your thoughts, advice and experiences are appreciated.


  2. alchemy
    Joined: Sep 27, 2002
    Posts: 13,072


    There was a lot of water port hole size and shape changes made between pre and post 48. Other than the single water hole that would need plugged at the front of the head, I would take a good long look at the rearmost holes. Not sure if you would want to use early gaskets or late gaskets.
  3. OK, thanks I will take a close look today. The 99 Mercury I am building is factory relieved and has been stroked to 4-1/8" using 21A rods. I have a couple of sets of early heads but none with the aluminum fins to give it a nicer finish. I thought of using the 8BA Flatattack or Kong heads I have. I will keep you posted on how I go.
  4. alchemy
    Joined: Sep 27, 2002
    Posts: 13,072


    You don't need finned heads on your 99A to be cool.

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  5. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,542

    Bruce Lancaster

    Look at it this way: First, skip the prewar 99 Gaskets that you can identify by big trapezoidal holes in center row. Ford called for these to be replaced with 59A gaskets for better distribution, the holes in central row are all round, and 99 heads were to be slightly redrilled slightly redrilled...and you don't need to drill since you are not using the early heads.
    Choice then is reduced to 59 heads or 8BA type.
    Next, study and worry thus:
    Early heads are designed to force water to both ends (rear slightly favored due to flow rate to get all the way aft) so water then flows to center where the exit is.
    Late heads are designed to encourage water to head all the way back in block and then all the way forward in the head to where the exit is.
    Next, look at both types for possible problems.
    You want to lay them on the block and study how the gaskets fit to the water flow are not directly interested in the water holes block because as in many other engines holes are designed for peculiar demands like getting casting sand out, and then the engineers tune the flow by gasket holes which are frequently much smaller than block holes. Obviously the gasket holes rule.
    I think the flow route differences will strongly encourage you to use the gaskets that match the clock, so you just really want to search for anything that would seem to discourage flow and perhaps drill anything like that.
    FlatJan likes this.
  6. 19Fordy
    Joined: May 17, 2003
    Posts: 6,000


    Short answer is "No".

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