Spark Plugs for Paxton?

slither

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I'm running stock Champion plugs with .032" gap. Mine's an '04 with stock Paxton pulley, Mopar cat-back exhaust and custom tune. I also installed an ATI damper and DLM intercooler for peace of mind. So far I've got about 6K on it with the blower and it runs perfect. Make sure you put the 8:1 washer and ring spacer in the FMU since you installed an aftermarket exhaust or it might lean out, which would not be good.
 

Racer Robbie

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Take a look at Autolite XP985 Xtream Performance plugs. We have been installing these on all the vipers that come into our shop, and we also supply them, though you can get them from NAPA or any parts store. They are an exact replacement for the stock plug and are iruidium. I do not know how they will work on a blown engine but as Slither says he uses the stock plugs above in his post these would be worth a try.
 

NoRice

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Mine had the Autolite 3923 in them until last week and now it has NGK 5691 which I believe are the Iridium.
 

GR8_ASP

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I used stock Champions last year and all was well (gapped to 0.032 as recommended by Paxton).

This spring I purchased iridium plugs. I installed them very early in the year, before I had a chance to "test" the power after a winter of memory loss. To say I was unhappy is a major understatement. Lost a lot of power (though not immediately perceived), idled like crap and in general was Bad with a capital B. The iridium plugs did not have the same reach as the stock champions. None I could find did. A dyno test confirmed the low power level (barely over 500 RWHP with the power peak all the way down at around 4000 rpm That is torque and power at low rpm was not affected but above 4000 was affected dramatically).

I installed new Champions, again gapped to 0.032 and picked up about 150 hp. Yes 150 hp! Iridium plugs looked fine when removed. I never had misfire codes or anything but it was clear that combustion was compromised. Power returned to 690 RWHP with power increasing right to red line.

Suffice to say I will not try iridium again unless they come out with the correct projection and heat range.
 

KepRght

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that is definitely the most pronounced example i have seen of incorrect heat range on a plug. 150hp down and the plugs look fine on removal. woah.
 

GR8_ASP

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I still have them. I will offer them at a fire sale price.

I was told by people that know the performance aspects of the Viper engine well that the combination of reduced extension (note it is about 1/4 inch shorter if I recall correctly) and heat range result in th eterrible high speed high pressure combustion.
 

NoRice

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I will have to look at the ones they just put in my car and get the exact # plug for you. My receipt says 5691 NGK which are the iridium, but that could be wrong. I can say that I did not loose power with them. As I ran against the same car 2 weeks in a row, 1st week with the Autolites and beat him by 3-4 lengths, 2nd week with the NGK's beat him by 5-7 lengths after he upped his boost by 5psi. There was also discernable difference in starting also after the plugs were changed, much easier to start now. Before it would take a couple seconds to start, now it fires immediately.
 

Viper X

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Hard to beat the stock plugs in a mostly stock eninge with a Paxton.

I run Denso Iridium IKH27 or IKH24 in the Stryker heads but wouldn't recommend them in a stock engine.
 

GR8_ASP

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Here is a picture of the iridium plug Denso suggested (IK16) on the top and stock Champion RC12ECC on bottom. Note the difference in tip projection. That is what is theorized for the power loss. Since none of the iridium plugs I have looked at indicate the tip projection distance I am very wary.

100_3125-small.jpg
 

NoRice

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Here is a picture of the iridium plug Denso suggested (IK16) on the top and stock Champion RC12ECC on bottom. Note the difference in tip projection. That is what is theorized for the power loss. Since none of the iridium plugs I have looked at indicate the tip projection distance I am very wary.

100_3125-small.jpg

My Autolites that I pulled out are not the protruded tip like your Champions show, mine are the reg tip as shown by your Denso plugs. Hmm, interesting stuff here. Who built your motor Gr8 Asp, or is it the stock motor with a paxton?

Art,
I was only charged 1 1/2hr labor to change my plugs and do a compression test on all cylinders plus the cost of the new plugs.
 

NoRice

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Hard to beat the stock plugs in a mostly stock eninge with a Paxton.

I run Denso Iridium IKH27 or IKH24 in the Stryker heads but wouldn't recommend them in a stock engine.

Are these the protruded or reg. tip?
 

Viper X

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The Denso's are regular tip similar to those pictured above. The spark plug location in the Stryker heads is a bit different that a stock head.
 

Viper TT/10

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My Autolites that I pulled out are not the protruded tip like your Champions show, mine are the reg tip as shown by your Denso plugs. Hmm, interesting stuff here. Who built your motor Gr8 Asp, or is it the stock motor with a paxton?

Art,
I was only charged 1 1/2hr labor to change my plugs and do a compression test on all cylinders plus the cost of the new plugs.


that is a great price for plug change and compression test. nice, no viper tax even though they are the only viper shop in vegas. nice to see garth is taking good care of you.
 

NoRice

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Art,
I was only charged 1 1/2hr labor to change my plugs and do a compression test on all cylinders plus the cost of the new plugs.


that is a great price for plug change and compression test. nice, no viper tax even though they are the only viper shop in vegas. nice to see garth is taking good care of you.

Garth takes real good care of me. :laugh: He's as straight up as they come, really honest and an asset for the Vegas guys. I thought the 1 1/2 hours was a good deal.
 

Racer Robbie

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Quote:
"Suffice to say I will not try iridium again unless they come out with the correct projection and heat range."

The Autolite XP985 is an exact replacement plug for the viper in the stock heat range and with the projected tip.
 
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