[mi_ked]

Hello I am looking at switching out the stock spark plugs on my V6, I read that the Autolite Spark Plugs Model # AP5143, are some good ones. I really don't know much about spark plug replacement, but hear that you can gain 20hp~ by changing the stock ones to platinum. Can anyone give me some insight; whether this would be a good idea, or is this an area to tread carefully in? Also any suggestions on what to get and what heat range and stuff would be great, thanks!

[fazm83]

You would be lucky to gain .5hp from spark plugs, the computer, the cumbustion, the spark voltage, resistance, is all setup for OE spark plugs, if you switch them out chances are you will lose power if anything. Just fyi, ford uses platinum (maybe even the double plats in the 4.0 since they use to in the explorers) for original equipment.

[ravenblack67]

I doubt you will gain HP by changing the OEM plugs. They are a very special plug and are designed for 100,000 Miles. Best HP gain is in the exhaust.

[echo7]

Yeah thats's prolly one of the few things ford doesn't skimp on, i know my dads explorer with the 4.0 has only had once replacement of spark plugs in its 130k life, and i think it was done just because of a tune up.

[fazm83]

the 4.0 explorers arent due for spark plug replacement until 100k. My moms explorer has 170k on it and only been changed once.

[Jetbo]

I have a friend that suggested that I should install some Bosch Platinum+4 plugs. He has them in his Focus and thinks they helped improve his overall power. I dont think it worth the hassle just yet but maybe someday.
http://www.boschusa.com/AutoParts/Sp...PlatinumPlus4/

[fazm83]

dont use bosch +4's unless your car is designed for them (IE c5 vettes, etc.) Ive seen cars that ran so poorly on them it would set rollin misfire's in some of the cylinders.

[JTGrant]

plat plugs are junk. They are only for longevity, actually a copper plug is better for performance. The only down side is that they need replacing much sooner. Get some copper plugs and start by setting gap about .010 larger than O.E.M(only if you are running N/A) you can gain hp off of playing with plug type, heat range, and gap. Believe me the only reason auto caompanies use plat plugs is for there longevity and reliablity. I would run a copper plug. But every car is different and reacts differently. My experience is that copper plugs ARE BETTER for PERFORMANCE. Some car run better on plat plugs and some do not. just my .02

[Riggs]

I'm not a spark plug expert myself but you will gain little to no power at all from spark plugs. The car will just run a little smoother and new plugs might last longer but no HP gain. I think most people want colder plugs though I can't be too sure all depends on stock, turbo, mods, etc.

[JTGrant]

Originally Posted by Riggs

I'm not a spark plug expert myself but you will gain little to no power at all from spark plugs. The car will just run a little smoother and new plugs might last longer but no HP gain. I think most people want colder plugs though I can't be too sure all depends on stock, turbo, mods, etc.

really no HP gain well I have seen it on the dyno

[andrewsg]

Ive been building motors since I was 11; dragging since I could do so on soapbox racers, etc etc.

And let me tell you -- I have never seen anything but trouble with the 'spark plug rage' that some shade tree mechanics go on.

Ive owned my fair share of n/a and boosted rides and let me tell you -- Ive had no problems EVER with sticking with the same manufacturer/type of plug that the vehicle called for from the factory. Granted if I was boosted Id go for a few steps cooler here and there -- but never anything more than a copper plug (you need to change coppers more often but to be honest -- I've never had anything but issues with plat plugs -- why? Because most vehicles dont call for them.. end of story).

-G

[Finn03]

Originally Posted by JTGrant

plat plugs are junk. They are only for longevity, actually a copper plug is better for performance.

It all depends on your setup. Plat. plugs are designed for longevity yes, but the motors are designed to run to the specs of the plug, resistance, heat range, stock gap, etc. If you have a built motor, and need a colder plug, thats one thing, to be honest though, the stock plug for a 4.0 is an AGSF24P, which is the EXACT plug as the AP5143, so unless the ink on the plug barrel is worth 20+HP, someones been misinformed.

The '05 motor might actually be running the AGSF24FM which is a finewire platinum, in which case it would be a downgrade to switch over to the ap5143. In certain cases it is true, copper can be better for performance, but in a mild V6 set to run platinum, with no major engine mods, your better off to stay with what you have.