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Unread 03-20-2012   #1 (permalink)
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Default Spark Plug Gap

Have a 2004 Mustang GT. In the process of purchasing a set of the Autolite 764 copper plugs for it. What is the gap for these plugs? Do these plugs come properly gapped from the factory?
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Unread 03-20-2012   #2 (permalink)
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According to my Haynes manual:

0.054 inch

Highly recommend you buy Motorcraft SP-493, they're Ford OEM and they're designed for your 4.6L modular engine... and they're pregapped
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Unread 03-20-2012   #3 (permalink)
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You should always double-check the gap anyway...
OP - what, if any, mods are you running? Performance oriented guys like to choose copper, but they won't last as long as OEM style plugs.
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Unread 03-21-2012   #4 (permalink)
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Quote:
Originally Posted by sillyrabbit0420 View Post
You should always double-check the gap anyway...
OP - what, if any, mods are you running? Performance oriented guys like to choose copper, but they won't last as long as OEM style plugs.
I bought the OEM platinum plugs (no one had the copper plugs around here) and they were pre-gapped at about 0.068", same as the old ones I took out of the engine (which were also Motorcraft plugs). I gapped the new ones to ~0.054" as recommended, and the engine runs smoother (I assume that comes from a combination of smaller gap along with brand new plugs).
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Unread 03-21-2012   #5 (permalink)
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Not running any mods, it's totally stock. Neighbor told me to make sure I get the copper plugs, and when I asked him why, he said, "just because", but that's not the answer I was looking for. Based on what a couple of you guys have said, it looks like I will be going with the Motorcraft SP-493 plugs at 0.054 gap. Thanks for the info guys.
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Unread 03-21-2012   #6 (permalink)
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Quote:
Originally Posted by 20GT04 View Post
Not running any mods, it's totally stock. Neighbor told me to make sure I get the copper plugs, and when I asked him why, he said, "just because", but that's not the answer I was looking for. Based on what a couple of you guys have said, it looks like I will be going with the Motorcraft SP-493 plugs at 0.054 gap. Thanks for the info guys.
Sounds like a good choice.
Copper plugs "only" last about 50k miles, while platinum often lasts 100k+ miles, but the spark in a copper plug is often more powerful as copper conducts electricity better than platinum, which is why many of us here prefer them over platinum.
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2003 Mustang GT
Exhaust: Mac O/R H-Pipe, Stock Catback.
Suspension: H&R Super Sport Lowering Springs, KONI STR.T Shocks & Struts, J&M Caster Camber Plates, Steeda Bumpsteer Kit.
Styling: Mach 1 Chin Spoiler & Grille Delete Kit, Spec-D Halo Projector Headlights, Sequential Tail Lights, 8" Black Antenna.
Audio: Pioneer DEH-X8500BH Receiver, Kicker CS68 Speakers (4x 225w).
Currently in storage in Florida.
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Unread 03-22-2012   #7 (permalink)
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As for the spark in the copper plug being more powerful, does this give you more HP, and less gas mileage?
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Unread 03-22-2012   #8 (permalink)
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Quote:
Originally Posted by 20GT04 View Post
As for the spark in the copper plug being more powerful, does this give you more HP, and less gas mileage?
I don't see how it does anything for mileage. If it does, then it would be a very insignificant amount that would be rendered immeasurable by the variation in driver habits from one person to the next. Your right foot determines your fuel mileage. Unless your car is a total hunk of shiz or you're one of those tards that ignores the fact that one of your tires is nearly flat.

Guys running S/C and NOS and turbo set-ups prefer copper plugs with a cooler heat range. We also run tighter gaps to prevent spark blow-out. Copper is a better conductor, so you get better spark. The downside is that the electrodes burn out more faster.

If your car is a mundane DD... then just slap OEM plugs in it. You'll see no gain from running copper plugs.
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Unread 03-22-2012   #9 (permalink)
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...Though I dunno. You might be one of those guys who swears the car gained 20 rwhp by switching to copper plugs. There are guys on here who have super sensitive butt-dynos that can tell hp increases by switching from 5w30 to 5w20.
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Unread 03-23-2012   #10 (permalink)
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Quote:
Originally Posted by sillyrabbit0420 View Post
...Though I dunno. You might be one of those guys who swears the car gained 20 rwhp by switching to copper plugs. There are guys on here who have super sensitive butt-dynos that can tell hp increases by switching from 5w30 to 5w20.
Cheesecake in the tranny fluid gives you 20rwhp.
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2003 Mustang GT
Exhaust: Mac O/R H-Pipe, Stock Catback.
Suspension: H&R Super Sport Lowering Springs, KONI STR.T Shocks & Struts, J&M Caster Camber Plates, Steeda Bumpsteer Kit.
Styling: Mach 1 Chin Spoiler & Grille Delete Kit, Spec-D Halo Projector Headlights, Sequential Tail Lights, 8" Black Antenna.
Audio: Pioneer DEH-X8500BH Receiver, Kicker CS68 Speakers (4x 225w).
Currently in storage in Florida.
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