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  1. #1

    Default Header collector studs - Help

    Wondering if anyone can tell me what the stock header collector studs are (thread pitch etc..) for an 86 5.0?

    I have a set of FMS headers that need new studs and I'd like to chase the threads first as well.

    I bought these:
    https://lmr.com/item/BBK-1571/Header...or-Bbk-Headers

    Are they the same? Will they work? I was able to screw one stud in, but it was awful tight and I don't want to force any others.

    Does anyone have a link to some new studs if those aren't the right size?
    "YEP, SITE'S BROKE"

  2. #2

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    I thought initially the collector studs were 7/16", and that they were changed later to 12mm. I don't know when that change took place though.
    1985 Mustang GT (Mothballed...Desired restomod parts acquired...Top of my project list for my 2024 retirement!)

  3. #3

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    I just ordered some 7/16''-14 studs from Napa. We'll see how those go.

    Hopefully I didn't F up the threads by hulking one of those BBK's in there
    It started to thread in OK just seemed to be pretty tight - I figured it was crud and rust in the threads, not the possibility of the wrong size

    It's ok, ya'll can laugh.
    "YEP, SITE'S BROKE"

  4. #4

    Default

    No laughing here.

    Did a little research and while RockAuto doesn't have a listing for 1986 (kinda odd that they're not listed there too, imo), but for 1985 they have an "Exhaust Flange Stud and Nut" listing, and it's showing it to be 12mm. Maybe those BBK bolts were right and like you said, just need a chase.

    https://www.rockauto.com/en/moreinfo...13936&jsn=1972

    Some thoughts:
    With a thread pitch so close - 14.0 tpi for the 7/16" and 14.514 tpi for the 12mm - I could see either one of them threading some distance in the other before the slight difference in thread pitch would rear it's head. However, the difference in diameters (nominally speaking; it's relative) - .438 for the 7/16" and .472 for the 12mm - I would think would allow the 7/16" to thread (rather loosely though, as thread fits go) into a 12mm female, but the 34 thousandths larger diameter (again, nominally) of the 12mm I would think would preclude it from threading at all into a 7/16" female.

    So based on what you did (getting a 12mm to thread in), I would assume that the 12mm is correct, because, as outlined above, I don't think it would have gone in at all into a 7/16" female. Let's see what happens when you try the 7/16". If my logic is correct, then the 7/16" should go in, but be sloppy, especially compared to the fit of the 12mm.
    1985 Mustang GT (Mothballed...Desired restomod parts acquired...Top of my project list for my 2024 retirement!)

  5. #5
    FEP Power Member
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    Default

    Try the 7/16" stud in the one good threaded hole and see how that works and go from there?
    Wonder if an old Motorsport catalog would say what size they are?
    '86 GT - weekend driver
    '86 Capri 5.0
    '86 Turbo Coupe
    '17 Mustang GT
    '23 BRONCO

  6. #6

    Default

    I got the studs this morning and they twisted right in the way you'd expect. Except for the one female I plowed the 12mm into....There's a litttttttle bit of play, but it does thread in and hold tight once it's tightened by hand, and even better with a wrench. I don't think it's enough to be concerned with. Let it be known that I blasted the header with a torch and really cranked on the 12mm BBK stud to get it in there LOL.

    LUCKILY the headers seem to be made of stronger material than the BBK studs, so the threads are OK, it's just the BBK bolt that got smushed from me hulking it in. Disaster avoided!!

    I read reviews on LMR about the BBK bolts and some folks said they worked with the FRPP headers, so I blindly trusted - Not the case.

    FUTURE REFERENCE FOR ANYONE:
    7/16'' 14 Pitch is what you want for FMS headers.


    Here's some snaps I found on the internet from a couple dif catalogs. It just says "Included", and "no modifications" so I suppose that's meant to read "same as the stock ones".



    Last edited by ITdude87; 06-13-2024 at 11:35 AM.
    "YEP, SITE'S BROKE"

  7. #7
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    Default

    I believe I used SAE Dorman studs on my 85.


    I looked it up in the Ford MPC,
    87 and up N804013-s2, AW-97-G M12 x 1 3/4" , 7/16 x 70 mm. Metric on one side and SAE on the other?
    80-86 388718-s2, WW-98-AH 7/16 -14 -14 x 2" hex shoulder for the Capri. No Mustang listing.
    Last edited by KevinK; 06-14-2024 at 02:42 PM.
    Fox Body/3rd Gen MCA Gold Card Judge
    84 SVO 24K miles, 85 Mclaren Capri Vert. 84 GT Turbo Vert.
    88 Mclaren Mustang Vert 20K miles, 89 Mustang LX Sport Vert,
    03 Mach 1 7900 miles, 74 Mustang II, 69 Mustang, 67 Mustang, 07 GT500,
    14 Mustang CS/GT, 15 F150 FTX Tuscany, 16 F250 Crewcab, 67 Tbird 47K miles

  8. #8

    Default

    Quote Originally Posted by KevinK View Post
    I believe I used SAE Dorman studs on my 85.

    If you have the Ford part number, I can look it up.

    I looked it up in the Ford MPC,
    87 and up N804013-s2, AW-97-G M12 x 1 3/4" , 7/16 x 70 mm
    80-86 388718-s2, WW-98-AH 7/16 -14 -14 x 2" hex shoulder for the Capri. No Mustang listing.
    I don't - But with the way the 7/16-14's fit, I bet it's safe to say they are the same as the Capri.
    "YEP, SITE'S BROKE"

  9. #9

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    Welp. A swing.... and a miss! Glad you got it figured out.

    These may be of interest to you....

    https://www.amazon.com/gp/product/B0...KIKX0DER&psc=1
    1985 Mustang GT (Mothballed...Desired restomod parts acquired...Top of my project list for my 2024 retirement!)

  10. #10

    Default

    @85GTGuy - That's exactly what I ordered from Napa - Thanks for that, and the additional information above!
    "YEP, SITE'S BROKE"

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