Stock spark plug gap discrepency

[jblc]

Referring to the technical manual, it says the following for stock iridium plugs (as indicated by 12405)
Spark plug: 12405
Spark plug gap: 0.0295 in (.75 mm)


But everywhere I look online, people say 0.030" - 0.032", with the "default" being 0.031.

Is the manual not to be followed?
Or does it not matter, because it's too close?

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[Loweredon33s]

It’s probably a difference in conversion from mm to inches. It’s stock, there’s a range because it’s not as critical, as long as it’s around .031” it’s fine. They wear and the gap increases, hence the range. In performance applications we run .025” without any issues. I mean, are we really talking about .0005” outside the internet range?

 

[Frenchy]

Because the factory plugs are an Iridium the only checking you should do is with your eyeball to see if it's crushed or not. If you use a gap checker and are not careful you will destroy the plug and will need to buy new ones.

 

[jblc]

Because the factory plugs are an Iridium the only checking you should do is with your eyeball to see if it's crushed or not. If you use a gap checker and are not careful you will destroy the plug and will need to buy new ones.

I see, thanks; I guess i'm used to older-style plugs and so may have made a mistake by checking
So pushing a 0.030 wire gauge through (some minimal / non-zero resistance) could have damaged it?
There was definitely some small pressure I needed to put on it, to push it through.

Is there a way to check?
I can certainly replace it with a spare if needed, as I haven't torqued the plug down yet.

 

[Frenchy]

When you look at the plus(when new) you will see the Platinum and iridium tips. If damaged they will most likely be missing

 

[jblc]

When you look at the plus(when new) you will see the Platinum and iridium tips. If damaged they will most likely be missing

Thanks. Ah, so it's either there, or missing. Sounds good -- i'll check.

 

[jblc]

@Frenchy Hmmm, the replacement plugs look different when I zoom in on the electrodes, both in electrode area, and color of both sides.

Did I get the wrong ones? Amazon said these Motorcraft SP578 are compatible with the 2021 ranger, so I assumed the part number was just an alternate Ford designation...

Stage3 also has these same ones here, so now i'm unclear whether the 12405 (per ford manual) or these are the correct ones.

And Advance auto parts has these which calls CYFS12YPT the same as SP578, but doesn't seem to relate to 12405.
The packaging on my new ones say CYFS12YPT.

 

[Loweredon33s]

Because the factory plugs are an Iridium the only checking you should do is with your eyeball to see if it's crushed or not. If you use a gap checker and are not careful you will destroy the plug and will need to buy new ones.

You can totally adjust the gap on iridium plugs. We do it daily. Gap tools are the first mistake. Feeler gauges and proper attention works fine. I have to gap iridium plugs for coyotes on every build and have maybe damaged three from using feeler gauges ever. We also gap ruthenium often with no problems.

 

[5thranger]

Referring to the technical manual, it says the following for stock iridium plugs (as indicated by 12405)
Spark plug: 12405
Spark plug gap: 0.0295 in (.75 mm)


But everywhere I look online, people say 0.030" - 0.032", with the "default" being 0.031.

Is the manual not to be followed?
Or does it not matter, because it's too close?

0.0295 would round out to 0.030 would it not so It looks like that 30 to 32 is a good range. Use a feeler gauge to check they should be about right out of box and use motorcraft plugs.

 

[jblc]

Use a feeler gauge to check they should be about right out of box and use motorcraft plugs.

Thanks; so it's okay to have a bit of friction with the feeler gage?

Anyone: any thoughts on the plug differences?

 

[Frenchy]

0.0295 would round out to 0.030 would it not so It looks like that 30 to 32 is a good range. Use a feeler gauge to check they should be about right out of box and use motorcraft plugs.

Only if extremely careful. Most individuals are not and that is why it's is not recommended to check gap on Platinum and Iridium plugs.

 

[Frenchy]

@Frenchy Hmmm, the replacement plugs look different when I zoom in on the electrodes, both in electrode area, and color of both sides.

Did I get the wrong ones? Amazon said these Motorcraft SP578 are compatible with the 2021 ranger, so I assumed the part number was just an alternate Ford designation...

Stage3 also has these same ones here, so now i'm unclear whether the 12405 (per ford manual) or these are the correct ones.

And Advance auto parts has these which calls CYFS12YPT the same as SP578, but doesn't seem to relate to 12405.
The packaging on my new ones say CYFS12YPT.

If not mistaken that is normal on Motocraft plugs

 

[jblc]

If not mistaken that is normal on Motocraft plugs

Thanks. Just to check, what is "that" referring to? The fact that the plugs look different, or that the part numbers don't match?

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