Spark plug question

Fast89GWILL · Dec 9, 2024

Pulled awsf42ca out of my 89 fox and the OEs are won't fit because of the diameter of the plug above the threads.

I bought the car as is and here these are used in GT40S. No clue what the prior owner may have done. All plugs the same.

Any ideas or thoughts and similar situations?

Thanks!

Mustang5L5 · Dec 9, 2024

The difference between the two plugs is the "W" in the part number, which refers to the threading length in the head below the seat. As you can see the AWSF is designed to reach deeper threads and the ASF.

Original plug for the GT40 iron head is the AWSF-32C (SP-447X).

You can use 42Cs but you need to get the AWSF-42C. The 42C's are a hotter spark plug

Jarhead67 · Dec 14, 2024

Fast89GWILL said:
Pulled awsf42ca out of my 89 fox and the OEs are won't fit because of the diameter of the plug above the threads.

I bought the car as is and here these are used in GT40S. No clue what the prior owner may have done. All plugs the same.

Any ideas or thoughts and similar situations?

Thanks!

Those plugs aren’t correct for GT40 heads

93gtmustang · Dec 15, 2024

Fast89GWILL said:
Pulled awsf42ca out of my 89 fox and the OEs are won't fit because of the diameter of the plug above the threads.

I bought the car as is and here these are used in GT40S. No clue what the prior owner may have done. All plugs the same.

Any ideas or thoughts and similar situations?

Thanks!

I just bought some plugs for my GT40-X303 heads.
The recommended plug for my heads in Motorcraft is AGSF32C. (SP-447-X, SP447, AGSF-32-X)
Autolite plug would be #104

Jarhead67 · Dec 15, 2024

Fast89GWILL said:
Pulled awsf42ca out of my 89 fox and the OEs are won't fit because of the diameter of the plug above the threads.

I bought the car as is and here these are used in GT40S. No clue what the prior owner may have done. All plugs the same.

Any ideas or thoughts and similar situations?

Thanks!

What heads do you have on your engine. The plugs you need are determined by the type of heads.

I have GT40 3 bar heads, the Motorcraft plugs I use are SP447. I recommend using copper core plugs

You can also use:
Autolite Spark Plug 104
NGK-TR55

None of these will fit GT40P 4bar heads.

Spark plug question

Fast89GWILL

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Mustang5L5

That is…until I whipped out my Bissell

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Spark plug question

Fast89GWILL

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That is…until I whipped out my Bissell

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