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  •  » FYI Ford, Classic Mustang Tech Discussion
  •  » GT40p heads and HiPO manifold spark plug question

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    4/25/2023 3:03 PM  #1

    BILLY WALTON from GEORGIA
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    From: CARROLLTON GEORGIA
    Registered: 4/14/2013
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    GT40p heads and HiPO manifold spark plug question

    What is your suggested spark plug and gap to run with these?

    Its really me....I fixed my caps lock .
     

    4/25/2023 3:47 PM  #2

    BobE
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    From: White Plains, NY
    Registered: 4/04/2013
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    Re: GT40p heads and HiPO manifold spark plug question

    Another factor is the ignition system you're running. 

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    4/25/2023 4:22 PM  #3

    BILLY WALTON from GEORGIA
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    From: CARROLLTON GEORGIA
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    Re: GT40p heads and HiPO manifold spark plug question

    Petronix flame thrower distributor and coil 
    1.6 roller rockers
    comp cams valve springs 26986 280 lbs
    Howards 221275-s roller cam
    forged flat tops
    Holley 570 Avenger
    24 inch radiator
    a/c
    p/s
    5 speed

    Last edited by BILLY WALTON from GEORGIA (4/25/2023 5:14 PM)

    Its really me....I fixed my caps lock .
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    4/25/2023 5:37 PM  #4

    BILLY WALTON from GEORGIA
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    From: CARROLLTON GEORGIA
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    Re: GT40p heads and HiPO manifold spark plug question

    seems like I ran Autolite Copper Core Spark ap 104 before in the 289

    Last edited by BILLY WALTON from GEORGIA (4/25/2023 8:06 PM)

    Its really me....I fixed my caps lock .
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    4/25/2023 5:57 PM  #5

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
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    Re: GT40p heads and HiPO manifold spark plug question

    I would use whatever a 1998 Explorer 5.0 engine uses. Gap at 0.060” assuming you have electronic ignition with a powerful coil.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    4/26/2023 3:34 PM  #6

    BILLY WALTON from GEORGIA
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    Re: GT40p heads and HiPO manifold spark plug question

    MS wrote:

    I would use whatever a 1998 Explorer 5.0 engine uses. Gap at 0.060” assuming you have electronic ignition with a powerful coil.

    It is showing AP 104 Autolites copper $4.69 each at oreillys and $3.49 at Autozone
    says gapped at 0.054 for 1998 Explorer.
    I ran by and grabbed 8 of them.
     

    Its really me....I fixed my caps lock .
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    4/26/2023 4:35 PM  #7

    Rudi
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    From: Stuck in the 50's Welland Ca
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    Re: GT40p heads and HiPO manifold spark plug question

    MS wrote:

    I would use whatever a 1998 Explorer 5.0 engine uses. Gap at 0.060” assuming you have electronic ignition with a powerful coil.

    WHAT!! 
    I guess that means I have been gapping mine incorrectly all these years.
    Mine are set to 40 thou with a Crane distributor, Hi six control  box and a Crane Fire Ball coil.
    I’m devastated, don’t know what to do, might need therapy!😱
    OBTW I’m using NGK 5 -1  plugs.

    Last edited by Rudi (4/26/2023 4:48 PM)

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

    4/26/2023 7:33 PM  #8

    Alan
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    From: Axtell KS
    Registered: 4/03/2013
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    Re: GT40p heads and HiPO manifold spark plug question

    Rudi, if you come to the bash, there is some late night therapy that will help you out.
     

    67 Coupe, 5.0 EEC IV Fuel injected. T5, 3:70 rear
     

    4/27/2023 11:25 AM  #9

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
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    Re: GT40p heads and HiPO manifold spark plug question

    Let me know if you can gap a plug at 0.054” exactly. My old worn out spark plug gapper can barely tell 60 from 45

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    4/27/2023 12:17 PM  #10

    Rudi
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    Re: GT40p heads and HiPO manifold spark plug question

    I have a few gauges, one is a wire type, the others are like a tapered ramp and I suppose feeler gauges are an option.
    I’ve never used a gapping  device, just the ground strap bending thingee on the wire gauge in conjunction with tapping the strap on my vies.
    Just out of curiosity what will the benefit going to .060” from .040”?
    Doesn’t increasing the gap retard the timing a bit or is it the other way round?

    Last edited by Rudi (4/27/2023 12:20 PM)

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

    4/27/2023 12:19 PM  #11

    Quicksilver
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    Re: GT40p heads and HiPO manifold spark plug question

    MS Hope your wife reads  this.. I see a stocking stuffier in the future.

    Money can't buy happiness. Butt it can buy Car Parts... and that is pretty much the same thing.67 FastBack
     

    4/28/2023 10:17 AM  #12

    6sally6
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    From: Surfside Beach,SC
    Registered: 4/02/2013
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    Re: GT40p heads and HiPO manifold spark plug question

    Rudi-Toodee......I believe the advantage is a strong/fatter spark because it is 'jumping farther' across to the strap.
    BITD....the old stocker coil could only jump a 32 thous. gap at best. The modern CD unit will knock your "d-ck-in-the-dirt" if you hold onto the plug wire while its running!!!( axe me how I know this!)
    Makes a funny taste in your mouth too!
    Anyhow.....that's why.
    (get good warz too)
    6sal6

    Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
     

    4/28/2023 1:09 PM  #13

    MS
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    From: Canyon Lake, Texas
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    Re: GT40p heads and HiPO manifold spark plug question

    So, THAT’S what happened…

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    4/28/2023 3:22 PM  #14

    red351
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    Re: GT40p heads and HiPO manifold spark plug question

    Well since we are getting a little off topic I will admit I like sticking my tongue on a fresh 9v battery. 

    Anyway years ago, taking the red car to our local 1/8 mile. It made no different with plug gap with the Pertronix.

     

    4/28/2023 6:38 PM  #15

    BILLY WALTON from GEORGIA
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    Re: GT40p heads and HiPO manifold spark plug question

    red351 wrote:

    Well since we are getting a little off topic I will admit I like sticking my tongue on a fresh 9v battery. 

    Anyway years ago, taking the red car to our local 1/8 mile. It made no different with plug gap with the Pertronix.

    What did you gap them at and what plugs did you use?
     

    Its really me....I fixed my caps lock .
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    4/29/2023 7:41 AM  #16

    red351
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    Re: GT40p heads and HiPO manifold spark plug question

    BILLY WALTON from GEORGIA wrote:

    red351 wrote:

    Well since we are getting a little off topic I will admit I like sticking my tongue on a fresh 9v battery. 

    Anyway years ago, taking the red car to our local 1/8 mile. It made no different with plug gap with the Pertronix.

    What did you gap them at and what plugs did you use?
     

    This is with the Cleveland. NGK-UR4GP come out of the box just shy 40 thous. I went up 50 making little to no  difference so settled with 40.

     

    4/29/2023 12:13 PM  #17

    BILLY WALTON from GEORGIA
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    Re: GT40p heads and HiPO manifold spark plug question

    gotcha

    Its really me....I fixed my caps lock .
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    4/29/2023 1:20 PM  #18

    Greg B
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    Re: GT40p heads and HiPO manifold spark plug question

    Does anyone know the fit of stock Mustang manifolds vs. spark plug clearance on P heads?

    If multiple things can go wrong, the one that will go wrong will be the one that causes the most damage.
     

    4/29/2023 6:40 PM  #19

    BILLY WALTON from GEORGIA
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    From: CARROLLTON GEORGIA
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    Re: GT40p heads and HiPO manifold spark plug question

    Greg B wrote:

    Does anyone know the fit of stock Mustang manifolds vs. spark plug clearance on P heads?

    I have  the hi.po
     

    Its really me....I fixed my caps lock .
       •Thread Starter
     

     

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