Quick question about spark plugs.

[USMCSHO341]

So I am just curious what the difference would be with gapping my factory spark plugs @ .30 versus buying aftermarket ngk replacements @ $7.50+ a piece. Is it really worth the swap? Do the ngk plugs come pre gapped if so what are they gapped at when I purchase them. And what are the downsides of gapping my factory plugs if any? Thanks for any help.


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[AJP turbo]

I would always check the gap on new plugs.....im still wondering why a gap change is required

Maybe people running meth could benefit from a tighter gap.

[BiGMaC]

So I am just curious what the difference would be with gapping my factory spark plugs @ .30 versus buying aftermarket ngk replacements @ $7.50+ a piece. Is it really worth the swap? Do the ngk plugs come pre gapped if so what are they gapped at when I purchase them. And what are the downsides of gapping my factory plugs if any? Thanks for any help.


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I have not seen any race, datalog, or dyno finding to indicate NGK or other being superior or inferior to MC OEM SP 534... It is important that they be the same heat range. Like ajp, I don't trust FMC or any other company's gaps because of the wide ranges I have found both in my car when I bought it and in AM plugs... I always check and put them as close to the desired gap as humanly possible. Both leading tuners recommend a smaller gap... OEM is .035... Tuners recommend .028 - .030. To prevent spark blowout at higher boost tunes the smaller may be better. Folks here are running both.

[USMCSHO341]

I would always check the gap on new plugs.....im still wondering why a gap change is required

Maybe people running meth could benefit from a tighter gap.

Same here. I plan on getting a LMS tune but am not sure why we need different plugs to run a tune.


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[AJP turbo]

If road racing or constant drag racing i could see 1 or 2 ranges colder but most of us street drive these cars and do wots occasionally or often but mostly u are not in boost..there is an optimum electrode temp and i think running these cooler plugs when street driving is not the way to go...ive never see one misfire with my stock plugs so far and ive hit 25 psi and have sustained wot pulls to 140 mph and 22 psi

[SHOdded]

Same here. I plan on getting a LMS tune but am not sure why we need different plugs to run a tune.


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As BiGMaC pointed out, narrower plug gap. is needed to prevent spark blowout in tuned turbo engines.  Also, to err on the side of a richer burn decreases the possibility of BOOM.

[AJP turbo]

But im still searching for the spark blowout...i have the same ignition system as everyone else.....i smell upselling

[SHOdded]

Hardly anything to upsell, though AJ   Plugs are an inexpensive item.

But for sure wouldn't mind a more technical explanation from our top tuners!

[AJP turbo]

Hardly anything to upsell, though AJ   Plugs are an inexpensive item.

But for sure wouldn't mind a more technical explanation from our top tuners!

Eh 30 here 50 there...

[USMCSHO341]

What brand/model plugs do you chaps use? After searching on orielly's and advance auto parts the choices are limited for my 10 SHO. And most were gapped at .035 the only option for anything lower was a set of ngk plugs gapped at .032 for close to $12. But when I searched for later year models like 2014 there were plenty of option gapped at .032 for way less. Shouldn't those plugs work with 10 as well?


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[SHOdded]

Motorcraft sp534's work fine, and word is they come gapped at 0.030 (great for tuned engines) from the factory.  As always, check with a gauge, that's the only truth that matters.

[Quinid]

All I know is I ignored torrie the day I received my tuner and went for max boost 93 tune. The stock plugs did NOT like it. The power would just randomly cutout for a split second at a time as it climbed the rpms at wot. The new plugs fixed it.

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[AJP turbo]

All I know is I ignored torrie the day I received my tuner and went for max boost 93 tune. The stock plugs did NOT like it. The power would just randomly cutout for a split second at a time as it climbed the rpms at wot. The new plugs fixed it.

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Most likely Torrie needed to revise your tune...And if you changed the plugs before you got your next tune and it fixed it then you had something seriously wrong with your other plugs....Or if you updated the plugs from what the 10's had then maybe the newer ford stuff is better.

There are a lot of reasons you can feel power cutting out when something is wrong with the tune

[Quinid]

All I know is I ignored torrie the day I received my tuner and went for max boost 93 tune. The stock plugs did NOT like it. The power would just randomly cutout for a split second at a time as it climbed the rpms at wot. The new plugs fixed it.

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Most likely Torrie needed to revise your tune...And if you changed the plugs before you got your next tune and it fixed it then you had something seriously wrong with your other plugs....Or if you updated the plugs from what the 10's had then maybe the newer ford stuff is better.

There are a lot of reasons you can feel power cutting out when something is wrong with the tune

They were the stock plugs on a 2010 with 70k miles. They worked great on the regular 93 tune.

Also I never had torrie revise the tunes.

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[AJP turbo]

It wasn't the plugs...You can choose not to believe it if you want