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Changing spark plugs gap.

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3.8K views 15 replies 10 participants last post by  ONEZ ST  
#1 ·
I got some new spark plugs coming tomorrow and my friend told me that a different gaps could add a little power to the engine. They come pre gapped at factory specs I was wondering if anyone has changed it and what seems to work the best.
 
#2 ·
That's theoretically possible. But I wouldn't change it unless you're planning on some extended testing, including before-and-after dyno runs and checking the plugs regularly.
 
#6 ·
Hey Boat, what does a "little power" mean to you? 5hp? I call BS on being able to feel it.

I have also heard you can make more power by clocking the electrode in the chamber.
I would assume that just like altering the gap, you would have to do a lot of testing to verify the sweet spot and gains made.

And I must also offer the obligatory "Manufacturer knows best" comment:
Don't you think if Dodge could get 5 or 10 more HP out of an engine by setting the gap a certain way, they would do it? Maybe they know that magical gap setting, but also know the plugs only last 15,000 miles when set that way?
 
#8 ·
Techically yes, wider gap, longer spark can increase power if you have the coils capable of throwing the spark. Stock coils have a set gap for a reason. Wanna larger gap, get different coils.



Indexing spark plugs.

This is also a much older trick. The idea was to index the open end of the electrode towards the intake valve, or center of combustion chamber for better flame front kernel. This too technically can add power when you are going all out.

They do make sparkplug washer to help with indexing. But on a stock car with twin plugs be hard pressed to see differance.
 
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#7 ·
I can’t remember the measurement exactly, but I did open up the gaps on the plugs for my ‘13 with a 345 about 0.015” per coil manufacturer specs. I had the S.O.S. coil packs on that engine.

I swapped them back to factory coils before trading the car and when I got my 392, but obviously didn’t swap plugs again nor regap them. On the way to dealership to trade, I noticed my ‘13 grew a larger set of nuts a couple of times that had me wondering WHAT did I do to gain that much more power?! And why didn’t that car act that way when I owned it?! LoL

Maybe it was the plug gaps? Maybe it was return to stock tune? (No more Diablo) Can’t say….


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#9 ·
Oh yeah, indexing a dual plug setup would SUUUUUCK! In car….

Just to elaborate further, you’d probably want the plug gap towards the intake, and center of the hemisphere, which means installing a plug deep into a hole, mark it, remove it, and install washer that sets it where you want the gap once installed again. Sixteen times! LoL!

Bad enough with 8. Definitely NOT an under hood job. Would need cylinder heads removed and on a bench for that to be best for indexing to me. My back will only allow 8 plugs before it hurts too much, so I have to work twice as fast to do the 16!


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#12 ·
I’m gonna swap plugs again. And I did put the S.O.S. coils on this 6.4L since I was changing the plugs anyway.

However, as opposed to getting Mopar plugs or even NGK’s, I chose the E3 plugs…..

Couldn’t gap those obviously.

But, feel like they’re whereby meant for the hotter coils? And, I notice the engine idle, in gear, like sitting at a stoplight, is only like 500rpm? I can tap the gas pedal just a touch and it goes to why appears to be 700rpm set point. At the next stop though, while idling with brakes held, it drops to 500 again.

Could that be the engine reacting to the coils?

Or am I seeing cam wipe starting?

Or is the TB and intake filthy and I need to grab some Mopar Combustion Chamber cleaner?


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#14 ·
Funny.