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Engine Correct Gap For 1991 Mustang GT With Motorcraft Plugs

  • Thread starter Thread starter Imatk
  • Start date Start date Jan 16, 2023
I

Imatk

Active Member
Apr 17, 2005
101
10
29
Jan 16, 2023
#1
  • Jan 16, 2023
  • #1
So looking here
https://lmr.com/products/79-93-fox-body-mustang-spark-plug-gap-specs

It shows that the correct gap for my car (completely stock) is .054

So that's what I set the gap to... BUT... then I realized the plug I was using is NOT the "ASF-42" since you pretty much can't find that plug anymore.

The one I installed was "ASF-42CA."

So I'm wondering if the gap is too large on the plug since it's not the same plug?

Or is .054 correct?

Car seems to be running correctly, but the gap on the plugs I pulled out was more like .045 or something (the dealer did the plugs last not me).

Thanks for any help!
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
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polk county florida
Jan 16, 2023
#2
  • Jan 16, 2023
  • #2
Your good.
 
I

Imatk

Active Member
Apr 17, 2005
101
10
29
Jan 16, 2023
#3
  • Jan 16, 2023
  • #3
Thank you!
 
F

FoxChasis

20+ Year Stangneter
Dec 23, 2003
589
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Jan 17, 2023
#4
  • Jan 17, 2023
  • #4
Same plug. Suffix 'A' just means a different manufacturer/supplier.
 
Reactions: General karthief

ALMOST STOCK

Founding Member
Sep 23, 2000
1,250
41
88
CA.
Jan 17, 2023
#5
  • Jan 17, 2023
  • #5
SPARK PLUG GAPPING

Ford Suggests .052--.056


autolite 24's
gap (factory setting) .054
 
Reactions: Potomus Pete

Gs1987GT

Active Member
Sep 25, 2019
484
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MidAtlantic
Jan 18, 2023
#6
  • Jan 18, 2023
  • #6
As noted, your good. Good work getting them changed out.

When I first bought my 87, it ran pretty well overall and I was happy with it. I knew i was going to do a full time when I installed the new headers and I could tell the motorcraft plugs in it looked very old.

When I pulled them I was shocked. They had to be the OEM plugs, they were worn so hard the gap was .90 plus! A prior owner installed an msd blaster coil which probably helped, but still. I was suprised it even ran at all, let alone as good as it did. Crazy stuff.
 
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