Confused about spark plug type
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Northstar Engines and System Technical Discussion Discussion, Confused about spark plug type in Cadillac Engine Technical Discussion; Hi........... I Just bought a 2000 Seville about 2 months ago. I had a 1990 Seville before and at 210,000 ...
  1. #1
    GrichG is offline Cadillac Owners Member
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    Confused about spark plug type

    Hi...........
    I Just bought a 2000 Seville about 2 months ago. I had a 1990 Seville before and at 210,000 I had to retire it. It still ran great and drove nice but the interior was cracked and looked pretty bad. After a tear or two I decide to look for another and was offered a great deal on the 2000.
    It has 88,000 on it so I thought I would look at the plugs (or at least find them). I bought a Haynes manual for it right away so I followed the instructions to find the plugs. Once I got under the "coil assembly"? and pulled out the rubber boots, sure enough there they were.
    I pulled out two of them and they looked pretty good, but I thought I would replace them any how. Since they are rated at 100,000 and I have 88,000 I figured it couldn't hurt.
    The problem is this, the plugs are AC 41-950's and my manual say's 950's were used in the 99's and that I am supposed to have 41-937's. Now my car was built 8/99 so it was one of the first 2000's build, so may be they just stuck some of the plugs in from the year before, but I don't know.
    I did a search on this site for 41-950 and found about an hours worth of reading, but a search on 41-937 yielded nada!
    Anybody know which plug I should put in there and why mine has an ?incorrect plug????
    Thanks

    BTW, the car is great. It felt substantially heaver than the 1990. It made my 90 feel like a sports car. I was a little disappointed until I pushed the throttle on this hard, then d..n did it move...........so, so long 1990 this is my new baby. I just need to make it corner better.

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    Ranger's Avatar
    Ranger is online now Cadillac Owners Member
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    Re: Confused about spark plug type

    According to the AC Delco site you need 41-987
    You can find their parts catalogue here.
    http://www.acdelco.com/html/pi_main_new.htm

  4. #3
    GrichG is offline Cadillac Owners Member
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    Re: Confused about spark plug type

    Thanks Ranger
    before I buy I'm going to need to know what the difference is in these plugs so i can make a decision. I'm sure that there is a web site some where that will detail what these numbers mean.

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    mtflight's Avatar
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    Re: Confused about spark plug type

    Word of caution:

    It seems that a lot of forum members have been unsatisfied when using aftermarket replacement spark plugs irregardless of the "specs."

    I'm sure Ranger would agree to go OEM, hence get the AC Delcos.

  6. #5
    GrichG is offline Cadillac Owners Member
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    Re: Confused about spark plug type

    I'm going to use the AC Delco absolutely. I've found a wealth of information on this forum about the different plug manufacturers.
    The question is; which to use
    AC Delco 41-950 or
    AC Delco 41-937 or
    AC Delco 41-987
    I'm sure they all cost the same.
    The plug type though seems to depends on where you go to get your information. So I still need to research to find the one I need.

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    mtflight's Avatar
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    Re: Confused about spark plug type

    Cool. Well I'm curious about the new Iridium ones and so on and so forth.

    What do the newest Northstars use? I would compare the newest (say on the 2006 DTS) with the one you have and then work from there.

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    Re: Confused about spark plug type

    I don't know what the differences are but I can tell you that when I did my '97, I remove 41-920's (or something like that). Apparently they where upgraded to 41-950's (which is what the AC Delco site called for, though my manual said differently). I would go with the 41-987.

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    Re: Confused about spark plug type

    GrichG, In response to your actual question...

    I personally do not know what may be the difference between the many different numbers you/they are finding. It could be something as simple as part number changes, different materials maybe? Or possibly different spark gap (I doubt that one, though)

    The best resource would probably be a dealership, although it would be hard to find one that will research it for you. A local auto parts store that carries Delco plugs may be willing, though.

    I know GM would be of no help. I've asked them a technical question before and they simply responded "The part in question is indeed the correct part".

    Irregardless, though. You are doing things correctly by using the plugs indicated by the manual. So, if you are unable to find the actuall information you are searching for, you can at least rest assure you have appropriate plugs in place.

    Dustin

  10. #9
    GrichG is offline Cadillac Owners Member
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    Re: Confused about spark plug type

    "The best resource would probably be a dealership, although it would be hard to find one that will research it for you. A local auto parts store that carries Delco plugs may be willing, though. "


    Trench
    That's a great suggestion. I actually have a great AutoZone not far from here. They are very helpful and usually have knowledgeable people working there.

    I guess my biggest concern is not knowing what a bad decision might do to the car.
    Thanks

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    Re: Confused about spark plug type

    The difference is probably the heat-range of the plug.

  12. #11
    mtflight's Avatar
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    Re: Confused about spark plug type

    Quote Originally Posted by GrichG
    "The best resource would probably be a dealership, although it would be hard to find one that will research it for you. A local auto parts store that carries Delco plugs may be willing, though. "


    Trench
    That's a great suggestion. I actually have a great AutoZone not far from here. They are very helpful and usually have knowledgeable people working there.

    I guess my biggest concern is not knowing what a bad decision might do to the car.
    Thanks
    In my experience AutoZone will push a brand name plug, because they don't even sell AC-Delco. They will tell you that the Bosch is a much better product, exceeding OEM. You will purchase them, and then your car will run "funny." Not quite bad, not as good... and they may suggest that you need new wires... they sell those too... etc etc

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    Re: Confused about spark plug type

    Quote Originally Posted by mtflight
    Word of caution:

    It seems that a lot of forum members have been unsatisfied when using aftermarket replacement spark plugs irregardless of the "specs."

    I'm sure Ranger would agree to go OEM, hence get the AC Delcos.
    I would agree too.
    Apparently when it comes to plugs, there is no which way or the other thing about it.
    Go OEM.
    Whatever the manufacturer recomends.

    Was reading an article the other day about "optimizing the fuel/air/spark mixture in order to allow everything to begin with a bang!"
    It was info about upgrading ignition systems, and what you may need to get you started.

    The people that wrote this article went to whom they believe, and say are,
    "one of the best known names in the spark business - MSD."

    After all the info that was written bout distributers, ignition control systems wires, and coils, etc....
    When it came down to plugs.
    What this company had to say was:
    "We recommend going with whatever the manufacturer says".
    "We stay clear of the fancy plugs out there."

    This is right from MSD.
    A company that has apparently "built its reputation on making a better spark".

    Another thing they said was that they "......Dont recommend platinum spark plugs because they dont dissipate the heat well, and since we're putting a lot more heat through the plug, it doesnt make for a very good combination."

    What I get out of that in general is to always go with what the manufacturer recomends. It looks quite clear and also makes perfect safe sense.

    Cant go wrong with what the manufacturer says

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