New Spark Plug Information for the 4.2L I6 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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  #1  
Old 09-27-2006, 05:16 PM
Crossroader Crossroader is offline
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New Spark Plug Information for the 4.2L I6

I was chasing down some plugs for my 02 TB and contacted ACDELCO.

Here's some interesting news I just got from ACDELCO concerning spark plugs for the Trailblazer. ACDELCO spark plugs 41-965 and 41-981 are being replaced by 41-103 (GM 12598004).

I am including the email I sent them and their reply. Know that this information has also been verified by calling their number at 1.800.223.3526.

---
My email to ACDELCO:

Hi,
My vehicle is a 2002 Chevy Trailblazer. In your on-line catalog you show
two spark plugs available for my vehicle - a 41-965 and 41-981. My question
concerns the interchangeability between the two plugs. Is the 41-981
replacing the 41-965? My vehicle came with 41-965 OEM with a .043 gap,
however, you're showing a .049 gap. ACDelco previous had .043 listed for
this plug then they changed it to .049. Which is correct and why the
change? What are the operating characteristics between the two plugs - heat
range, etc? Any and all info you can give between the two plugs would be
greatly appreciated. Thanks, John.
---

---
Here is their response:
Thank you for writing ACDelco, John.
We appreciate your e-mail regarding the spark plug for your 2002 Chevrolet
TrailBlazer. Please know the 41-965 and 41-981 spark plugs have been
discontinued.
Be aware the 41-103 Iridium spark plug is the recommended spark plug for
your vehicle. This spark plug should not be deviated from preset gap.
We are sorry that we cannot be of more assistance with this inquiry. If
further assistance is required please call our representatives at
1-800-ACDelco (1-800-223-3526). They are available from Monday through
Friday, from 8 a.m. until 8 p.m. Eastern Time, for your convenience.
Thank you for your interest in ACDelco.
ACDelco Customer Assistance
---

The ACDELCO plug 41-103 is also used on the 2006 Trailblazer. The tech I talk to on the 800 number verified that both 41-965 and 41-981 are being replaced by the new plug and that production has stopped for those numbers. You can still use the previous numbers if the parts are available. I also asked if the 41-981 replaced the 41-965. The tech said yes but could not answer why the gaps had been changed for the 41-965.

*Note that info this is only for the 4.2L I6 engine.

So I guess they've answered by quest for the plug I will be installing in my TB!
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  #2  
Old 09-27-2006, 09:31 PM
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Blazernut Blazernut is offline
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I got the same news today from the shop I buy parts from. I said 103! What? And they said "new numbers, the old ones are being dicontinued!"

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  #3  
Old 10-25-2007, 01:24 PM
epescina epescina is offline
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So what should the gap be? I have the 103's.
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  #4  
Old 10-25-2007, 01:27 PM
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Quote:
Originally Posted by epescina View Post
So what should the gap be? I have the 103's.
According to the GM reply in the previous post, the gap is set and should not be changed.
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  #5  
Old 10-25-2007, 01:40 PM
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Sounds like they are going to the iridiums to replace the older 965-981 platinum plugs. Iridium (the metal) is about 1/3 the cost of platinum and performs as well if not better so I suspect that's the reason. Simplifies parts inventory too.

I've been running the 41-981s with the .043 gap they came set at in my 2002 and it runs and idles perfectly. A narrower gap will be a little easier on the coils too. Less voltage needed to jump the gap.
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  #6  
Old 10-25-2007, 04:24 PM
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joe_jeep joe_jeep is offline
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dont belive the gap is set! thats a joke! make sure the gap is correct. they get damaged in shipment all the time.
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  #7  
Old 10-25-2007, 04:29 PM
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I gapped mine at .045 and its never ran better. I went with the Delco's as well.
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  #8  
Old 10-25-2007, 04:51 PM
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Quote:
Originally Posted by joe_jeep View Post
dont belive the gap is set! thats a joke! make sure the gap is correct. they get damaged in shipment all the time.
Yep. Good point to check the gaps first. I checked mine before I put them in to verify they were all the same.
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  #9  
Old 10-25-2007, 04:59 PM
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2Xtreme 2Xtreme is offline
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Quote:
Originally Posted by superman_79065 View Post
According to the GM reply in the previous post, the gap is set and should not be changed.
You should never trust that a plugs preset gap is accurate.

Plugs move around in their boxes and cases of boxes get manhandled/dropped/etc. and could effectively close the gap some.

ALWAYS check that the gap on a 'pregapped' plug.

With that being said, what are the 41-103's pregapped to at the factory?
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  #10  
Old 11-25-2007, 01:45 AM
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prostude prostude is offline
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Quote:
Originally Posted by 2Xtreme View Post
You should never trust that a plugs preset gap is accurate.

Plugs move around in their boxes and cases of boxes get manhandled/dropped/etc. and could effectively close the gap some.

ALWAYS check that the gap on a 'pregapped' plug.

With that being said, what are the 41-103's pregapped to at the factory?
the 41-103's are the new irridium plugs
thye are supposed to be gapped at .043

I found that my plugs where between .039 and .041 so pretty close

the old ones where the original with 110k and varied from .045-.060 looked like I could have left them for another 50k or so
I changed them and the car runs a little stronger (less gas pedal pressure equals more power)
I am hoping for a 1-2 mph increase
BTW the new plugs only say irridium on the side in small letters ont box
at least these plugs are very easy to change compared to some other cars out there today
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