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  1. #1
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    Ford FE exhaust flanges

    OK, theoretical question time!

    The Ford FE I'm having built has Edelbrock heads, which have the "16-bolt GT pattern" bolt pattern, like this:


    If I get the exhaust built by someone else, though, I'll need to drop off my 'buck' engine as a pattern, which has the 8-bolt non-GT pattern iron heads on it, which look like this:



    For another view - iron heads on my 390 on the left, Eddy heads have the right hand bolt pattern:


    The 8-bolt pattern works with two of the bolt locations in the 16-bolt heads and the ports etc are at the same height (I believe, must double check - Eddy heads are currently at the engine builder, though), and I have a set of 8-bolt flanges.. would you:

    a) Use 8-bolt flanges (per non-GT heads) and leave two bolt positions un-filled
    b) Use 16-bolt flanges, which I'd have to import, but mock them up on the 8-bolt heads

    Given it's likely to be four completely separate primaries (including flanges), I'm not sure the extra two bolts per port will help much anyway, so I'm tempted to just have them made up on the 8-port heads..


    Hm.. Dave, what do you fit to your engines, head & flange wise? KevW, what about you?


    Sometimes I wish I'd taken the easy option and thrown a Chevy 350 in like everyone else used to Certainly would have been cheaper!
    Last edited by aaronjb; 15-03-18 at 02:30 PM.
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  2. #2
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    8 bolt. As per....
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  3. #3
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    8 bolt (2 per cylinder). And don't cheat on the quality of the fasteners
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  4. #4
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    Thanks fellas Somehow it seemed silly to ignore the extra holes, since they're there on the Eddy heads and there's not a lot I can do about that.. but 8-bolt flanges are way easier to get in the UK, should I need a set! (I do have an old set already that might be salvageable, actually)
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  5. #5
    Join Date
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    According to my books on the subject, Ford went form the 8 hole to a 14 hole as it was difficult to install the lower bolts on some car models. The lower two bolt holes for the center ports were not present.

    Later on, the Cobra-Jet heads received the 16-hole pattern so that a choice could be made dependant on the car model the engine was to be installed in.

    So, either configuration was deemed appropriate.

    As the 8-hole system always worked well, as it does on my FE, I see no reason to burden yourself with 16-hole flange plates.
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  6. #6
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    If you did a drawing of the 16 bolt flange, I’m sure your local laser cutter could knock you a set up for a few pounds.

  7. #7
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    Quote Originally Posted by Eggbert View Post
    According to my books on the subject, Ford went form the 8 hole to a 14 hole as it was difficult to install the lower bolts on some car models. The lower two bolt holes for the center ports were not present.

    Later on, the Cobra-Jet heads received the 16-hole pattern so that a choice could be made dependant on the car model the engine was to be installed in.

    So, either configuration was deemed appropriate.

    As the 8-hole system always worked well, as it does on my FE, I see no reason to burden yourself with 16-hole flange plates.
    Thanks John! Incidentally, which book was that? Probably one I have already but haven't read properly

    Quote Originally Posted by cperry View Post
    If you did a drawing of the 16 bolt flange, I’m sure your local laser cutter could knock you a set up for a few pounds.
    True that, I wish I had done it before they went off to the rebuilder 100 miles away, as I know a tame laser cutter nearby.. Hindsight!
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  8. #8
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    Quote Originally Posted by aaronjb View Post
    Thanks John! Incidentally, which book was that? Probably one I have already but haven't read properly
    It was Steve Christ's book "How to Rebuild Big-Block Ford Engines: https://www.amazon.ca/How-Rebuild-Bi...s=steve+Christ

    I found similar information in a few other FE Engine books, one even mentioning the alternate bolt holes were to make it easier to install exhaust manifolds due to little clearance with the shock towers.

    Incidentally, I also looked at many pictures of original Ford cast iron exhaust manifolds. Some had vertical bolt holes, some had the more-or-less horizontal holes and one even had a combination, 2 horz holes on three of the flanges and 2 vert holes on the aft flange. I'm not saying no engine used all 16 holes, but every picture I have seen only used 2 bolts per flange for a total of 8 bolts per cylinder head.

    Barry Rabotnick's book does mention that the extra holes with larger flanges (presumably on custom made headers) helps where exhaust porting has left limited area for the header flanges to cover the ports. Although I might be a bit confused as he also mentions slotting the header flanges to adjust the fit.

    My cylinders heads only have the vertical holes and the custom headers are slotted. I find it useful as I can install the bottom bolts, then slide the header onto the bolts which holds it in place when installing the upper bolts.
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  9. #9
    Join Date
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    Use the 8-bolt version, and get 8 individual flangen of 10mm thickness.

    While I am at it: I use the 3/8"NC to 1/4"NF ARP studs with serrated nuts. If all is plane you won't even need a gasket.
    Well, I didn't. For more than 7 years after which I sold that car.

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