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Discussion Starter #1 (Edited)
Here is some info I obtained today regarding spark plugs.

We have a ton of customers who use 1 step colder plugs on their srt8's for use with strokers or Superchargers or basically any combination that nets them around 500rwhp. The plug most often used is listed below.

NGK-LZTR6AIX-13- Stock number 2315- 1 step colder for 6.1
Projected tip, Iridium

Now that we have been porting 6.4L heads left and right, I have a ton of 6.4L spark plugs in a box and I wanted to determine how they compared. Here is that part number.
NGK-LZTR6AP-11EG

The 6.4L plug is the same heat range as the 2315 plug listed above which makes it a good plug for 500rwhp applications. The differences are that the 6.4L plug is platinum and not iridium, it comes gapped at .044" instead of .052" like the 2315 plug above and it has a 10k ohm resistor instead of a 5k ohm resistor. Evidently 5k is industry standard but 10k is supposed to increase plug life.

Anyhow, just wanted to let everyone know that there is a new option available for a 1-step colder srt8 plug for 500rwhp applications. This will not work with the Eagle cylinder head as it has a washered seat plug and not a tapered seat plug like the 6.1 and 6.4.
 

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Discussion Starter #2
For Eagle Heads
Stock Eagle Plug: NGK SPLZFR5C11
1 Step Colder: NGK ILZFR6D11 (Stock #1208) or NGK LFR6AIX-11 (Stock #6619)
1.5 Step Colder: Brisk ER14YS
2 Steps Colder: NGK LFR7AIX (Stock #2309)

Eagle plugs at top and Apache/6.1 plugs on bottom.
 

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So for the guys that are getting Apache heads, like myself, do they make colder plugs yet?
 

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Discussion Starter #4 (Edited)
6.4 and 6.1 use same style.

Brisk- RR14YS: 1 step colder for 6.1 (450-525rwhp)
NGK-LZTR6AIX-13: 1 step colder for 6.1 (450-525rwhp)
Brisk- RR14S: 2 step colder for 6.1 (525-650rwhp)
NGK-LTR7IX-11: 2 step colder for 6.1 (525-650rwhp)
Brisk- RR12S: 3 step colder for 6.1 (650-775rwhp)
Brisk- RR10S: 4 step colder for 6.1 (775-900rwhp)

Those hp estimates are just a guideline. Each combo has its own unique characteristics and spark plug requirements.
 

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Does Brisk not make a 2 step colder plug?
 

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6.4 and 6.1 use same style.

Brisk- RR14YS: 1 step colder for 6.1 (450-525rwhp)
NGK-LZTR6AIX-13: 1 step colder for 6.1 (450-525rwhp)
Brisk- RR14S: 2 step colder for 6.1 (525-650rwhp)
NGK-LTR7IX-11: 2 step colder for 6.1 (525-650rwhp)
Brisk- RR12S: 3 step colder for 6.1 (650-775rwhp)
Brisk- RR10S: 4 step colder for 6.1 (775-900rwhp)

Those hp estimates are just a guideline. Each combo has its own unique characteristics and spark plug requirements.
The plugs don't look like they will interchange to me, one is a tapper seat and the other is a crush washer. Plus the length from the sealing area (crush washer/tapper seat) to the top is a different length also which could cause a the coil packs not to reach properly.
 

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Hey Andy I'm gonna be putting in a 125 shot nitrous express kit that is on it's way to me. People or saying I need a 1 step colder plug. What plugs to I use???


Sent from my Autoguide iPhone app
 

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Discussion Starter #9
The plugs don't look like they will interchange to me, one is a tapper seat and the other is a crush washer. Plus the length from the sealing area (crush washer/tapper seat) to the top is a different length also which could cause a the coil packs not to reach properly.
The top plug is an Eagle plug, the bottom plug is an Apache/6.1 plug. He asked about spark plugs for an apache head which is the exact same style as a 6.1 head. The Eagle is what is different.
 

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Discussion Starter #10
Hey Andy I'm gonna be putting in a 125 shot nitrous express kit that is on it's way to me. People or saying I need a 1 step colder plug. What plugs to I use???


Sent from my Autoguide iPhone app

Brisk- RR14YS: 1 step colder for 6.1 (450-525rwhp)
NGK-LZTR6AIX-13: 1 step colder for 6.1 (450-525rwhp)
NGK-LZTR6AP-11EG: 1 step colder for 6.1 (450-525rwhp)
 

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Thank u can u get from you?? And is nitrous ok with my cam?


Sent from my Autoguide iPhone app
 

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Hey Andy,

I see you have the following listed as a 2 Step colder plug for a 6.1 engine.

(6510) NGK-LTR7IX-11: 2 step colder for 6.1 (525-650rwhp)

How come I see the following part number on Bwoodys site as a 2 step colder plug?

NGK (5107) LZTR7AIX-13 Iridium IX Spark Plug

Which is the correct part number for a NGK Iridum 2 step colder plug?

Thanks!
 

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Discussion Starter #14
Hey Andy,

I see you have the following listed as a 2 Step colder plug for a 6.1 engine.

(6510) NGK-LTR7IX-11: 2 step colder for 6.1 (525-650rwhp)

How come I see the following part number on Bwoodys site as a 2 step colder plug?

NGK (5107) LZTR7AIX-13 Iridium IX Spark Plug

Which is the correct part number for a NGK Iridum 2 step colder plug?

Thanks!
http://www.jegs.com/i/NGK-Spark-Plugs/739/LZTR7AIX-13/10002/-1?parentProductId=830899

http://www.jegs.com/i/NGK-Spark-Plugs/739/LTR7IX-11/10002/-1

According to Jegs, both are Iridium
LTR7IX-11: Projected and .044" Gap
LZTR7AIX-13: Extended projection and .052" Gap
 

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Discussion Starter #16
So they are both correct as being a 2 step plug for a 6.1 engine then? If not which is the correct one we should be using if you want a 2 step colder plug for a 6.1 engine?

Thanks!

If it has a 7 in the part number, its 2 steps colder. OEM is a 5.
6 = 1 step colder
7 = 2 steps colder
4 = 1 step hotter
 

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If it has a 7 in the part number, its 2 steps colder. OEM is a 5.
6 = 1 step colder
7 = 2 steps colder
4 = 1 step hotter
Ok Thanks Andy! So which one would you get for a Jeep running 10 psi of boost?

Sorry to keep beating this one to death Andy. Do you know what the difference between Projected vs. extended projected would be and in what type of application they are needed?
 
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