Stock: SP Gap .40 or .54??

madonionrs · Apr 19, 2004

Spark Plug gap, 1989 Mustang .. stock

93tealstang · Apr 19, 2004

Anywhere from .52 to .56 should be ok.

p.exeter_bleu · Apr 19, 2004

if i remember i think its supposed to be .58?

madonionrs · Apr 19, 2004

Thanks guys!

This is probl why my car is idling like hell, I have it at .40 with no dielectric grease.

FoxChasis · Apr 19, 2004

Stock gap is .054".

And you don't use di-electric grease.

madonionrs · Apr 19, 2004

FoxChasis said:
Stock gap is .054".

And you don't use di-electric grease.

What ?
I thought you use anti-seize on the end that goes in the block (threads)
Then di-electric grease on the tip that goes into the spark plug wire.

TattooMatt · Apr 19, 2004

madonionrs said:
What ?
I thought you use anti-seize on the end that goes in the block (threads)
Then di-electric grease on the tip that goes into the spark plug wire.

That is correct. Stock recommendations for gap in my 93 operators manual is .50-.54

p.exeter_bleu · Apr 19, 2004

ah crap, i was told .58 does the year make a difference? what should i be gapping my 89 at?

madonionrs · Apr 19, 2004

You should use di-electric grease on the tip of the plug that goes into the wire boot, correct?

ram360 · Apr 19, 2004

madonionrs said:
You should use di-electric grease on the tip of the plug that goes into the wire boot, correct?

You should. If you buy new plug wires it already has it in the boots.

5spd GT · Apr 19, 2004

So what happens if you don't put the dielectric grease on when you change plugs...(stayed with my 9mm FR wires)...should I take the wires off and apply some grease to the ends...I just recently put in Autolite 25's gapped at .054...

In short what happens if you don't put the grease on the ends?...

Luvmy88 · Apr 19, 2004

Would adding an Accel super coil call for an increase/decrease in plug gap?

TattooMatt · Apr 19, 2004

I'm pretty sure that the gap would be the same for an 89. It's the same engine there are only slight differences between them. .50-.54

If you don't use di-electric grease you will have a chance that the plugs could arc. It's basically an insulator and a water shield. You'll have an easier time getting your wires off the plugs next time if you use it too.

madonionrs · Apr 19, 2004

Btw, are you supposed to just put a thin layer on.... or put a good swab of it on the tip.

TattooMatt · Apr 19, 2004

madonionrs said:
Btw, are you supposed to just put a thin layer on.... or put a good swab of it on the tip.

Just make sure it's covered pretty well. I don't think that it's a super accurate procedure. Just put enough so that the wire won't seize on the plug after some damp weather.

FoxChasis · Apr 19, 2004

My mistake....thought you were talking about the threads. I totally forgot about the plug wire-to-plug connection.

If I remember correctly (I'll have to get into my Motorcraft spark plug catalog later to confirm), all H.O. 5.0L Mustang engines except the '86 model year spec'd a gap of .054". The '86 model year H.O. 5.0L Mustang engine spec'd a gap of .045". (The plugs were unique for '86 as well.)

5.0guy · Apr 19, 2004

yeah, I've been wondering about this too--if anyone has a stock car, with the coil cover, look on that, mine is messed up and I couldn't read it. I'm runnin around .04 gap--I think..

cevtv · Apr 19, 2004

Actually, it's .044" up until 1990. 1991 to 1993 is .054". They used a higher ouput coil starting in 1991.

iwashmycar · Apr 19, 2004

Luvmy88 said:
Would adding an Accel super coil call for an increase/decrease in plug gap?

Not sure if this Q was answered yet....
I'd like to know also?

cevtv · Apr 19, 2004

Well, if the factory opened the gap when they went to a higher output coil, then it makes sense that you could open it a bit with a higher output Accel Supercoil.............

Stock: SP Gap .40 or .54??

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