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Thread: Spark plugs question

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    Default Spark plugs question

    Ok guys, pulling the heads off my 96 buick century station wagon 3.1 liter. I am going a little crazy in what spark plugs should I replace the old one...I'm stuck between AC Delco 41-902 or the Bosch #4540 or even the AC Delco 41-940...I am a big factory oem type of guy but...
    Your thoughts please
    Last edited by CenturyMan; 09-12-2016 at 02:02 PM.



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    Personally I wo stick with ac delco or whoever is making their spark plugs. Last time I got some NGK was making them so you could get either and they would be the same, just different writing on them. I ended up with ac delco because I got a great clearance deal off rock auto. I don't see any right now going on though.

    As for what type to go with, I tend to stick with what the car came with since that is what it is set to use. So if your car was built for copper got with the copper, if built for platinum go with the platinum.

    according to this chart from ac delco, http://www.rockauto.com/en/moreinfo....1016165&jsn=12

    copper has a lower melting point and lower lifespan, but stronger spark. How I see it, I wouldn't want a weaker spark, and since it the old plug didn't have issues with melting, I didn't find that an issue, and life span I was also ok with especially since copper ones were cheaper.
    Last edited by lemons bob; 09-12-2016 at 03:43 PM.

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    Senior Member Century7667's Avatar
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    Quote Originally Posted by CenturyMan View Post
    Ok guys, pulling the heads off my 96 buick century station wagon 3.1 liter. I am going a little crazy in what spark plugs should I replace the old one...I'm stuck between AC Delco 41-902 or the Bosch #4540 or even the AC Delco 41-940...I am a big factory oem type of guy but...
    Your thoughts please
    Here's what a set of Delco 41-902 look like after 150,000 miles:

    http://www.a-body.net/forums/showthr...gins-LIM/page6

    No engine drivability issues before I removed them.

    Ken T.

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    Senior Member Duke George V's Avatar
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    Yeah, I used 41-940s in my L82 before I popped it. Ran great.
    Daniel
    Kaiser George IX: 1996 Buick Century Special wagon. 214-SFI. 194k miles. Never gonna give you up, never gonna let you down. First documented LX9 swap in an A-body! Click here to read my build thread!
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    Quote Originally Posted by lemons bob View Post
    I tend to stick with what the car came with...
    Overall, this is a good practice, especially when coils and wires have not been renewed, with OEM quality merchandise.

    On two redblock Volvos I own, I installed OEM wire set (Bougicord), Bosch cap/rotor, and on one a new coil, and I have not had an issue with Bosch Iridium plugs. OEM plugs are copper-tops, and these newer type plugs may require higher voltage when gapped at 0.060. If a plug has normal gap of OEMs copper plugs, I don't think there will be an issue.

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    Senior Member Drop Top Olds's Avatar
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    I would not consider copper plugs with the current spark plug options available. A 96 model year was most likely running a platinum plug. With GM vehicles avoid Bosch. AC or NGK would be good brands to consider.
    1959 Chevrolet Apache 31 235 I-6 SM420
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    Senior Member turbokinetic's Avatar
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    Remember with the DIS system, there is one coil for each 2 cylinders. The sparkplugs and coil are in a series circuit. This means that one plug fires with the tip electrode as positive, and the other fires with the tip electrode as negative. Why does that matter? Because the amount of erosion is vastly different depending on the spark polarity. Three plugs will erode the ground electrode, and three will erode the center electrode.

    The original plugs have a platinum contact point on BOTH the ground and the center electrode, so no matter which direction the current flows, it always will fire against a protected surface. Make sure you get a plug with the ground electrode protected as well as the center. If not, you won't realize the full life of them. Several manufacturers sell them like this.



    In my opinion, for a daily driver, ACDelco, Nippon Denso, NGK, Autolite seem to be good choices.

    For high powered, turbocharged, engines the only thing I will run are ACDelco standard copper plugs, with cut-back ground electrode.

    I have personally had unsatisfactory results with Bosch and Champion plugs.

    Hope this helps!

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    Senior Member Duke George V's Avatar
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    I've heard seasoned mechanics say Champions are just barely fit for usage in lawnmowers...

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    I have been using wal-marts autolite plugs in my old celebrity. even through all the crap over the past 3 years those spark plugs have hit th 30k mark and still work. I suspect one or 2 of them are starting to get worn or a wire is bad, it misses under low rpm load usually when cold. still. they are technically due for replacement and they are $2 and some cents for every 2 plugs. 3 years? can't complain

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