Regap factory plugs. Go 3/10ths faster!

[redline727]

I was thinking after I read what the OP said the gap is supposed to be it sounded low. I remember when I installed my coils on my 13, stock was around .50. And Performance Distributors recommended .52-.55 with higher power coils. Maybe it changed on the 15? So I checked the latest updated HTML user manual on the Ford owners site and this is what the gap is supposed to be stock, per Ford Not .41-.45. So if you're going to change it I would go by this unless recommended otherwise by your tuner for some reason. What was your source OP?

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[Excelerater]

I was thinking after I read what the OP said the gap is supposed to be it sounded low. I remember when I installed my coils on my 13, stock was around .50. And Performance Distributors recommended .52-.55 with higher power coils. Maybe it changed on the 15? So I checked the latest updated HTML user manual on the Ford owners site and this is what the gap is supposed to be stock, per Ford Not .41-.45. So if you're going to change it I would go by this unless recommended otherwise by your tuner for some reason. What was your source OP?

The funny thing is when I yanked my plugs once side of the motor was
low 50s the other high 40s...No matter what ford says which holds little value to me I would look to the plug MFG....

 

[redline727]

The funny thing is when I yanked my plugs once side of the motor was
low 50s the other high 40s...No matter what ford says which holds little value to me I would look to the plug MFG....

Why would what Ford says hold little value to you? They engineered the engine...and the stock plugs are Motorcraft...

 

[Rubred50]

I checked my plugs and they were consistently over gapped at .057. The owner's manual, pg. 265, recommended range is .049-.053, which is reported above. Everyone is challenging the OP but I must commend him for his finding... stop looking for reasons to bash him and recognize his respectable catch. Looking back, my car had a ruff item until it was tuned. This may have been the reason why. Ford should make sure the plugs are set properly from the factory and this conversation would be moot. GREAT FIND OP, THANK YOU!!!

 

[bluebeastsrt]

I checked my plugs and they were consistently over gapped at .057. The owner's manual, pg. 265, recommended range is .049-.053, which is reported above. Everyone is challenging the OP but I must commend him for his finding... stop looking for reasons to bash him and recognize his respectable catch. Looking back, my car had a ruff item until it was tuned. This may have been the reason why. Ford should make sure the plugs are set properly from the factory and this conversation would be moot. GREAT FIND OP, THANK YOU!!!

Thank you! The point of the thread is not to mislead anyone but to get information out there and motivate people to check their plugs if they feel the car isn't performing 100% properly. Of course DA plays a part in the better slip. But like I stated earlier my friends car. picked up MPH from the service a month before the DA got to where it is now. Interestingly he is running the same 115-116 in early September that he runs in mid October. Your always going to have some guys that try to take a crap on anything even when your trying to help others out. If I was worried about being the fastest guy on the fast list. I would keep any information that would help others out all to my self!

 

[WhiplashGo]

Thank you! The point of the thread is not to mislead anyone but to get information out there and motivate people to check their plugs if they feel the car isn't performing 100% properly. Of course DA plays a part in the better slip. But like I stated earlier my friends car. picked up MPH from the service a month before the DA got to where it is now. Interestingly he is running the same 115-116 in early September that he runs in mid October. Your always going to have some guys that try to take a crap on anything even when your trying to help others out. If I was worried about being the fastest guy on the fast list. I would keep any information that would help others out all to my self!

I agree with you. Thanks for sharing the insight & not being selfish.

 

[Cascadia_302]

The funny thing is when I yanked my plugs once side of the motor was
low 50s the other high 40s...No matter what ford says which holds little value to me I would look to the plug MFG....

This^ as my prior post (19) mentioned....must certainly be understood as well.

 

[christian]

I really appreciate the info here and everything that may help my Mustang run better and or more efficiently.


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[Higgs Boson]

I think as enthusiasts it is important to make sure things are right on our cars, the plug gap included....in fact, I will be verifying all my plugs are at .050 as soon as I have a chance to pull them. Without this thread, I never would have checked, so thank you to the OP for pointing this potential irregularity out to fellow members. Sincerely.

With that said, if one thinks going from .058 to .050 is going to pick up what is essentially 30 HP, you might get yourself tested.... ;-)

Could the spark be blowing out at .057? Maybe.....but Density Altitude is indeed the holy grail to power production, no one can argue that unless you just really don't know what you're talking about....but then, we could all argue all day about things we don't understand! Once you have the correct information, there are no more arguments.

 

[Norm Peterson]

This might be very interesting to some of you guys who like me. Did mods and didn't feel they were doing the same for you as others. Anyway. I have a buddy that has a 3.55 Auto car just like me with the same CAI and tune. He started throwing codes and took the car in for service. After two days of looking they replaced his spark plugs. They also told him that the gap on the plugs was way off from the assembly line. He was trapping 111-112 before the plug change and 115-116 after. My car was not throwing codes but also seamed stuck in the 112 trap speed even after I had added a CAI & tune. So I took my spark plugs out and regapped them. They were also quite a bit off from the factory. Correct gap is supposed to be .041 to .045! The factory gapped plugs were .055 to .058! Well long story short. I ran the car again tonight and picked up 3/10ths and almost 3 mile per hour. The car is now trapping 115 from a simple re gap of the spark plugs.:frusty:

Hmmm . . . sounds like this sort of thing might help my peak speeds on the longer road course straights . . . thanks.

Just a thought - ever try cutting the side electrode back so that it does not extend past the center electrode?


Norm

 

[bluebeastsrt]

Hmmm . . . sounds like this sort of thing might help my peak speeds on the longer road course straights . . . thanks.

Just a thought - ever try cutting the side electrode back so that it does not extend past the center electrode?


Norm

No I've never thought of that. But I picked up an extra set of plugs from my tuner on the cheap and It wouldn't hurt to try it.

 

[Norm Peterson]

FWIW, I've found that filing seems to be the best method, with the file ground smooth on the face that would be on the center electrode side. Just be sure to break any little burrs off the side electrode as you finish up.


Norm

 

[Waldorf]

Hmmm . . . sounds like this sort of thing might help my peak speeds on the longer road course straights . . . thanks.

Just a thought - ever try cutting the side electrode back so that it does not extend past the center electrode?
Norm

I've done it before with auto transmission cars. Rounded off the ground electrode so that the end is even with the center of the "hot" electrode. Helps with low end and mid range throttle response using the same plug gap. Big difference using the "buttt dyno" and made for ~.1 second better 0-60 time using an old G-Tech. Only tried on N/A engines though. Always used just the plain old copper plugs... no exotics. My brother tried a set in his Mustang drag car (5.oh pushrod 5 speed)... no real difference in ETs. Your mileage may vary.

That is all...

 

[Ramen]

Pull my plugs and they were all .050" on the money. Oh well, it was still nice to get intimate with my GT and peace of mind is priceless.

 

[Waldorf]

Pull my plugs and they were all .050" on the money. Oh well, it was still nice to get intimate with my GT and peace of mind is priceless.

Agreed... will be pulling mine and checking just for giggles. Also got lucky today... mine was built before the 16's who will be recalled for seat belts.

That is all...

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