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Fox Body Mustang Spark Plug Gap Specs (79-93)

Last Updated 11/1/2018 by Jason Konieczny

When tuning up your Mustang or even adding forced induction, proper spark plug gap is key. Check out this Fox Body spark plug gap guide to ensure your plugs are properly gapped!

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Whenever working on your Mustang, whether it is 200,000 miles or it is a new car, you always want to have proper spark plug gap! This article will cover the spark plug gaps for Fox Body Mustangs over the years to ensure your Fox will produce the most efficient spark to ignite the air-fuel mixture!

A larger gap is more efficient as it provides a larger spark for a Naturally Aspirated Mustang. When adding a Power adder, Supercharger or Turbocharger, you want a smaller gap. The Spark Plug Gap has to be reduced so the increased turbulence and pressure in the combustion chamber can ignite quicker and more intense. When the Spark Plug Gap remains larger under a boosted application, a Misfire can result due to the spark being blown out

Fox V8 Mustangs were equipped with ASF or AWSF spark plugs. From 1982 to 1985, the High Output (H.O.) version of the 5.0L used one heat range colder.


Year

Engine

Motorcraft Number

Gap (inches)

1979

5.0L (49 – State)

5.0L (California)

ASF-52

ASF-52-6

.050

.060

1980

4.2L (all)

ASF-42

.050

1981

4.2L (all)

ASF-52

.050

1982

4.2L (all)

ASF-52

.050

1982-85

5.0L Carbureted

5.0L CFI

ASF-42

ASF-52

.044

.050

1986

5.0L H.O.

AWSF-34

Or 44

.050

1987-93

5.0L H.O.

ASF-42

.054

1993

5.0L GT-40

(Cobra)

AWSF-42C

.050


1979-93 Mustang Spark Plugs