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

Created by Jason Konieczny
Last Updated 5/17/2021

When tuning up your Mustang or even adding forced induction, a proper spark plug gap is key. Check out this Fox Body spark plug gap guide from LMR!

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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 a proper spark plug gap! This article will cover Fox Body Mustangs Spark Plug Gaps 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 like a 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 intensely. 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.


Fox Body Mustang Spark Plug Gap Guide

Year Engine Motorcraft Number Gap (inches)
1979 5.0L (49 States) | 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 AWSF-44 .050
1987-93 5.0L H.O. ASF-42 .054
1993 5.0L GT-40 (Cobra) AWSF-42C .050