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post #1 of 14 Old 07-11-2010, 11:08 AM Thread Starter
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which spark plugs for stock heads?

just as the title says... stock 1986 5.0 with a turbo pushing at most 10lbs.

this is in my 95. msd ignition and blaster coil. stock distributor.

i was going to run what i have read to run, which was autolite 3923's, but was just told:

"You do realize that a 3923 autolite is not a tapered seat plug? Its a flat seat with a washer. Stock heads take a washerless tapered seat plug. Therefore a 3923 wont work in a stock head."

so now im wondering what plugs to run and at what gap?


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post #2 of 14 Old 07-11-2010, 12:40 PM
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Now that we have this, threads titled "which plug for this" will not be tolerated. #

Thanks to Chris the idea and to Brade for his input.

Spark Plug FAQ

Stock Heads also (Dart Windsor Jr & Sr)

Naturally Aspirated (non-projected tip)
NGK
Specifications:

Thread Size= 14mm
Hex Size= .625
Reach= .46
Seat Type= Tapered
Electrode= V-Power

NGK R5673-6 Stock Number 2405 (1 heat range hotter)
NGK R5673-7 Stock Number 2817 (Factory heat range)

Naturally Aspirated (non-projected tip)

Specifications:


Thread Size= 14mm
Hex Size= .625
Reach= .46
Seat Type= Tapered
Electrode= V-Power

NGK R5673-6 Stock Number 2405 (1 heat range hotter)
NGK R5673-7 Stock Number 2817 (Factory heat range)

Autolite Stock Heads

Autolite 25 Naturally Aspirated
Autolite 24 1 Heat Range Colder
Autolite 23 2 Heat Ranges Colder

Autolite Race Series for Stock Heads

Autolite AR135 Naturally Aspirated Only
Autolite AR134 1 Heat Range Colder
Autolite AR133 2 Heat Ranges Colder


NGK Forced Induction

NGK-Non Projected Electrode
Specifications:

Thread Size= 14mm
Hex Size= .625
Reach= .75
Seat Type=
Electrode= V-Power

R5673-8 Stock Number 3249
R5673–9 Stock Number 3442 for tons of boost and power.

Aftermarket aluminum heads (TFS, Edelbrock, AFR, Canfield, Brodix)

NGK Forced Induction

R5671-A8 Stock Number 4554, 1 heat range Colder (up to about 600rwhp)
R5671–A9 Stock Number 5238, for 18+psi, 2 heat ranges colder 650+ rwhp
R5671–A10 Stock Number 5820, for race cars.

Autolite Forced Induction and N/A

Autolite 3924's Naturally Aspirated Only
Autolite 3923’s 1 Heat Range Colder, good for approx 550rwhp
Autolite 3922’s 2 Heat Ranges Colder, good for approx 650rwhp

Autolie Race Series for aftermarket heads

Autolite AR3935 Naturally Aspirated Only
Autolite AR3934 1 Heat Range Colder
Autolite AR3933 2 Heat Ranges Colder

Plug Specs for GT-40 Iron, GT-40 Aluminum, GT-40X, & GT-40P Heads

Thread Size- 14mm
Hex Size- .625
Reach- .708
Seat type- Tapered
Electrode- Standard Nickel
Projected Tip

The stock equivalent replacement part numbers according to the Motorsport Catalog are:

Ford MotorSport Part Number AGSF-32C for the GT-40 Aluminum, and GT-40X
Ford MotorSport Part Number AWSF-32C for the GT-40P, and GT-40 Iron

These plugs cross to:

NGK - BPR6EFS Stock Number- 3623 (Stock Heat Range)

Autolite- 104

These are the NGK Race Series Part numbers and specs:

Thread Size- 14mm
Hex Size- .625
Reach- .708
Seat type- Tapered
Electrode- V-Power
Non-Projected Tip

NGK- R5724-8 Stock Number- 7317 (1 Heat Range Colder)
NGK- R5724-9 Stock Number- 7891 (2 Heat Ranges Colder)
NGK- R5724-10 Stock Number- 7993 (3 Heat Ranges Colder)

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post #3 of 14 Old 07-11-2010, 12:46 PM Thread Starter
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already read that and maybe im just retarded, but it doesnt help me

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post #4 of 14 Old 07-11-2010, 01:40 PM
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Run the ar134 plug or just autolite 24s
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post #5 of 14 Old 07-11-2010, 09:33 PM
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Im running the autolite 24 gapped at 22
post #6 of 14 Old 07-12-2010, 06:08 AM Thread Starter
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my question now is, the stock autolite plug that the autozone website says to use is a autolite 2545, but the 2543 is two steps colder. or 2544 one step colder. the only difference between these plugs and the autolite 24/23 is the thread depth. why should i go with the shorter thread depth plug like the 24/23 over the 2544/43, which is the stock length?

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post #7 of 14 Old 07-12-2010, 12:08 PM
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Just run what we have listed... There is a reason for that lol
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post #8 of 14 Old 07-12-2010, 03:52 PM Thread Starter
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Quote:
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Just run what we have listed... There is a reason for that lol
ok so whats the reason to run a shorter plug?

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post #9 of 14 Old 07-12-2010, 09:01 PM Thread Starter
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ok so heres my thought, let me throw this out there and see what people think. stock lengh plugs autolite 2545 have a 18.00mm thread depth. but the plugs im being recommedend to use which are autolite 24's have a thread depth of 11.60mm. meaning the spark will be more off to the side of the combustion chamber.

why would i want this? is it because with boost and the higher air flow in the chamber, being off to the side is less likely to blow out the spark?

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post #10 of 14 Old 07-12-2010, 11:40 PM
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Wrong plug gap will cause spark blowout

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post #11 of 14 Old 07-13-2010, 07:09 AM Thread Starter
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Quote:
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Wrong plug gap will cause spark blowout
i realize that...but still doesnt answer my question...whats the reason to use the shorter plug???

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post #12 of 14 Old 07-25-2010, 09:35 PM Thread Starter
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just to give a litte up date. i have answered my own question. well the reason why i SHOULD NOT have gone with the autolite 23's is because they do NOT work with 1986 heads. they work with 82-85 and 87-95. NOT 86. for some reason, god only knows why ford does these things, but the shorter autolite 23 will not reach into the threads of the head. so today since no local parts store stocks the plugs i need, i had to order them. the stock plug for the 1986 head is an autolite 2545. one step colder is a 2544 and two steps colder is a 2543. which is the plug i ordered.

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post #13 of 14 Old 07-25-2010, 10:02 PM
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Do you have 86 model heads on your 95 model car?
post #14 of 14 Old 07-26-2010, 08:30 AM Thread Starter
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Without going into a lot of detail. Here is my current set up. Picked up a stock 1986 long block over the winter. Freshened it up, and threw it in my car. I have gone through a few different motors over the years. This is the latest "budget" build. So yes I have 1986 heads on my 1986 short block in my 1995 car.

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