Engine Correct Gap For 1991 Mustang GT With Motorcraft Plugs

Imatk

Member
Apr 17, 2005
97
10
19
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!
 
  • Sponsors (?)


Gs1987GT

Active Member
Sep 25, 2019
484
186
53
MidAtlantic
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.