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OEM Spark Plug

The original OEM Spark Plug FOR the 2001 Mustang GT came with the Motorcraft AWSF-32P

This is how the Motorcraft OEM plugs decodes.

Thread Diameter A = 14mm
Reach W = .708" (.288 Short Travel)
Plug Characteristic S = Suppressor (Carbon)
Plug Characteristic F = Conical Seat
Heat Range 3 = 3 Cold
Tip Configuration 2 = Extended (Power) Tip
Plug Characteristics P = Standard Platinum Electrode

The plug recommened by Ford has changed through years and currently it is the AGSF32PM
This is how the current recommended (7/2011) plugs decodes

Thread Diameter A = 14mm
Reach G = .708" Conical Seat
Plug Characteristic S = Suppressor (Carbon)
Plug Characteristic F = Conical Seat
Heat Range 3 = 3 Cold
Tip Configuration 2 = Extended (Power) Tip
Plug Characteristics P = Standard Platinum Electrode
Plug Characteristics M = Nickel Plated Shell

So if we compare the plugs the changes are
1. The Thread reach was extended from a "half thread" to a "full thread"
2. They added a "Nickel Plate Shell"

A note on the half thread and full threaded plugs. A lot of people believe that the new plug, that has the FULL THREADS on it are there because of the spark plug blow out problem, that Ford has had through the years.

But if you just think about it for a second, the extra threads do NOTHING. There are 6 threads on the OEM spark plug. So at the MOST, they will engage 6 threads inside the head. You can not screw the plug in anymore because of the concal shoulder on the plug, so the new threads above the half threads (on the spark plug) do NOTHING.

Below is a picture so you can see where the extra threads are compared to the threads in the head. You still have the same number of threads, (6 or less) that hold the plug into the head.
There is nothing there for the extra threads to thread into. IF there were something there to thread into the OEM plugs with the UNCUT threaded shoulder would not have been able to thread into the head all the way. This is why they mention that you can use a FULL thread in a half threaded head but you can NOT use a half threaded plug in a FULL threaded head.

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