Spark plug options

[jtoddk98]

What would be the best gap on a stock tune? Getting plugs changed at my 45k oil change next week.


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[ZSHO]

I would go with 0.35 with a stock tune to be on the safe side,good luck.

[jtoddk98]

Can I use the sp534 plug instead of the 528? I have a 2011 car


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[Brucelinc]

Can I use the sp534 plug instead of the 528? I have a 2011 car


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Absolutely.  If stock, gap at .035.  Tuned gap at .030. 

[BiGMaC]

Good info shoboat. I wish I knew more about ignitions or at least more details on coils and such. Cause narrowing the gap has its draw backs as well. Wider gaps have faster and flame propagation, but I have yet to see any spec's on the stock coils or even after market ones. And would more voltage allow you to run a larger gap and not have spark blowout. Ive seen testing on how spark gap has a big effect on efficiency and emissions.

Yup, and also idle quality. I have noticed that the idle is a touch rougher at .30 than .32.
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I wish we could readily find this data... And I wonder if there are parameters beyond timing that the ECM controls related to spark.  I my SP534s are gapped at 0.30, but I have experimented with gap due to slight vibration at idle which resolves with an extra 100 rpms at .030... Interestingly this is only after the O2 sensors are warm and the slight vibration is not present in open loop operation when I start cold initially.  This resolves at the increased gap of .032.  I stayed at .030 based on Dan's recs.

[crash712us]

Yeah my  idle is a little rough also. Has been this way for as long as I can remember. Not really a issue though.


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[ShoBoat]

Good info shoboat. I wish I knew more about ignitions or at least more details on coils and such. Cause narrowing the gap has its draw backs as well. Wider gaps have faster and flame propagation, but I have yet to see any spec's on the stock coils or even after market ones. And would more voltage allow you to run a larger gap and not have spark blowout. Ive seen testing on how spark gap has a big effect on efficiency and emissions.

Yup, and also idle quality. I have noticed that the idle is a touch rougher at .30 than .32.
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I wish we could readily find this data... And I wonder if there are parameters beyond timing that the ECM controls related to spark.  I my SP534s are gapped at 0.30, but I have experimented with gap due to slight vibration at idle which resolves with an extra 100 rpms at .030... Interestingly this is only after the O2 sensors are warm and the slight vibration is not present in open loop operation when I start cold initially.  This resolves at the increased gap of .032.  I stayed at .030 based on Dan's recs.

The stock SP534 plugs were actually gapped at .32 from Ford. Hence why I didn't have the vibration. I began noticing the same as you described when I went to .30 with the NGK plugs. Isn't the stock gap for the 13+ .30?


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[crash712us]

Not that I am aware of, still .35 as far as know.


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[Brucelinc]

Manual says .033-.037 on SP528s for a 2013 SHO. 

[ZSHO]

Changed plugs at 15k,right before my trip to south,installed SP-534 ,they came pregapped ao 0.32 and installed them cause was in hurry,car seems to run smoother than at 0.30 with same plugs but notived better fuel economy gapped at 0.32??

[BiGMaC]

Manual says .033-.037 on SP528s for a 2013 SHO. 

Strange.... Mine came with SP534s ... But we've found a number of things like this in the "combo" manual Ford puts in the glove boxes of both MKSs and SHOs.... Even features not available on SHO at all, LOL

[ZSHO]

Manual says .033-.037 on SP528s for a 2013 SHO.

MY original SP-528 which came from the factory were gapped at 0.35-0.37.

[ZSHO]

Manual says .033-.037 on SP528s for a 2013 SHO. 

Strange.... Mine came with SP534s ... But we've found a number of things like this in the "combo" manual Ford puts in the glove boxes of both MKSs and SHOs.... Even features not available on SHO at all, LOL

MY Manuel said car has SP528,which it had on there.

[Brucelinc]

The plug type must depend on the build date.  The 2014 manual calls for SP534s gapped at .033-.037. 

[kinder]

Manual says .033-.037 on SP528s for a 2013 SHO.

MY original SP-528 which came from the factory were gapped at 0.35-0.37.

The plug type must depend on the build date.  The 2014 manual calls for SP534s gapped at .033-.037.

Yup... whet to 534during the '13 run.