Hey guys, quick question. Im swapping my plugs out after 104k miles... i know i was bad an probaly shoula had it done sooner... but, what kinda plugs should i get, its bone stock so what do you guys think.
Spark plugs
prozx3
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This is what I run, but have some people say they run .60 or even .65 sometimes, anyone have input on that?
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Trial and error is all you can do there. Ideal performance is subjective to a point but there are also slight variances in each individual engine. I tried mine at .050 first and it was better but not as smooth as .055. In my opinion, .060 is too much cowbell but that's just me.
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Autolite 104s are dirt cheap (less than $2 a plug), copper core, and run better than pretty much anything out there. You can't beat that. Like TolusD said, gap them to .050 - .055 and you're golden. People have tried the more expensive NGK TR7s, Denso Iridiums, and other high dollar plugs only to come right back to the 104s. They're about the best out there, especially for the price.
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what about staying with the stock double plats ??
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There really isn't a point when they are 2-3 times the price of the 104s and the 104s run better. Also, the 104s can be found at any autozone or advance vs having to go to a dealership for the motorcrafts and a lot of times them not having them in stock. At least that typically the situation at the dealers near me.
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hmm im not sure what to do now because im basically due to change mine and I was going to hit steve tousley up for a set. I guess i dont know what kind of mileage you get out of 104's but i sure like the 100,000 mile double plats.
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I'm running Autolite 103 coppers (colder spark 103s since I'm boosted) and I still get 32-34mpg highway with being boosted and a 4.06 final gear. If anything, mpg improved with them. The copper plugs are more conductive and less brittle than platinum which makes for more resistence to heat and detonation while providing a more responsive spark. Whether you are bone stock or have a 600+whp built monster, Autolite coppers work amazing in our cars.
As for longevity, they don't last as long. I wouldn't suggest going more than 15k miles on them but when they cost less than $8 for 4 of them, that's dirt cheap. I change mine every other oil change but I'm also boosted and beat on my car so they take more abuse.
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For the cost and time of replacing 104s only after 15k miles, to me it seems like it would be more cost effective just to go with a stock set of plugs.(for my application)
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Time? It takes 15 min and that includes gapping. lol To each their own. You'd be spending $8 once a year, if that.
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well today i changed them, got the 104's an gapped them to .055. as it stands right now the best thing i did to the car ( havent done much). but when taking the old plugs out, cylinder 1, and 2.... I think have issues i dont know tho. cylinder 1's plug was rusted out at the threads, and cylinder 2's had oil in the threads. also the other one's from 3 and 4 where wayyy off with the gap the first 2 were gapped i think at .052 and the others were .057 and .058? i guess its just fords crappy factory workers....
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That's the effects of platinum plugs over time. The metal is more brittle and therefore known to have the gap open up or close over time. They may have all started at .045 gap but have ended up where they are now. As for the oil, as long as you are not seeing oil out of your exhaust, you are fine. Sometimes the valve cover gaskets on the Duratecs will leak a little bit and that oil my drip down by the plug and get on the threads. The rust is normal really, especially for having been in there as long as they were. Some moisture can get by the boots of the COPs and that combined with the heat in the head will make them rust.
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yea the guy at autozone was like the plats are the way to go scince their oem, an i was like i have heard they suck an never but iridium or platinum. then he said i will lose gas milage if i go to copper an the spark wont be as hot? is that true, i was just thinking he was trying to talk me into the more expensive plug scince they were 6 per plug vs 2 dollars of the 104's.
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They don't create more heat. No matter the spark plug metal, the heat range of the plug is controlled by the resistor. You will see higher temps from platinum and iridium plugs compared to coppers of the same heat range resistor but this is not because their heat range is higher. Whether the plugs are Copper 104s or Iridium XP104s, the heat range is the same. What sets them apart is that copper is better at dispersing heat than both platinum and iridium. Copper is both more conductive and less brittle therefore it's much easier to gap them and have them stay gapped for their lifespan.
Basic horsepower 101 says that more heat typically equals more power. This is a good rule of thumb but is not always true and can vary depending on your engine setup. Too much heat results in detonation which usually results in engine failure. For high compression or forced induction applications, copper plugs are commonly used because the heat dispersion properties helps with knock resistance allowing for more power to be made, and because the more conductive properties of the copper helps to keep the spark from being blown out. The majority of the boosted guys on here use Autolite 103 copper plugs (one step colder than the 104s).
Platinum plugs are good for longevity, but they sacrifice strength and knock resistance. Copper plugs are good for strength and knock resistance, but they sacrifice longevity and ability to make high heat. Iridium plugs are good for high heat and higher octane, but sacrifice knock resistance and strength. Silver plugs are good for knock resistance, higher octane, higher heat, and resistant to corrosion, but sacrifice strength and longevity. Silver plugs are usually very exspensive and are pure race applications only using corrossive fuels such as methanol. I think Accel actually makes a set for the Duratec.
Why are Autolite coppers so good in our cars? Well... they just are. lol Even on a bone stock car, it's been a known fact that the coppers run smoother and seem to make more power.
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I believe that the working electrodes are not copper, Just the metal inside the ceramic. Believe me, a spark that can jump l/4 inch isn't going to be slowed down by a steel allow electrode....
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Looks like ill be buying autolite 104's. pretty convincing haha 
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Autolite dbl plats (or NGK, for that matter) have lower resistance than the 104 coppers do... it's a small difference, but at high rpms that means something. The dbl plats generate less internal heat, due to the lower resistance. Also, changing them far less often saves the threads on aluminum heads. If your engine is stock or close to it, dbl plats can't be beat... for price (last much longer), for performance (resistance), or for security (thread protection).
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Please explain to me then why the copper 104s have proven to perform better with the Duratecs in numerous trials over the years? I've seen twice as many double plats come apart and fail than I have coppers.
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What "proof" would that be? A Duratec is an internal combustion system like every other engine, there is no special magic that causes a Duratec to "need" copper plugs. If a boosted Duratec (or Zetec, SPI) runs better on copper than dbl plats, that's cool... but an NA Duratec is just an NA Duratec. For that the factory choice is best. And I've seen Iridium electrodes erode away, but I've never seen a dbl plat fall apart in a stock engine.
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