AC Delco spark plugs
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I have two vehicles with the 3.4L engine (Silhouette and Grand Am) and have heard the best plugs to use are either the AC Delcos or NGK Iridiums (part number TR55IX). I've heard problems with Bosch platinums (especially the +2 and +4, but also with the regular platinums).
I recently purchased the OEM AC-Delco plugs for our '02 GM minivan. The base of the plugs clearly has "NGK Made in Japan" stamped on them. They look to be a version of the NGK Iridium spark plug made for AC-Delco.
Remember, AC-Delco doesn't actually *make* much of anything any more.
John
Remember, AC-Delco doesn't actually *make* much of anything any more.
John
I replaced the factory Delco Platinum plugs in my S-10 when it started to idle rough. 3 of the 6 plugs where missing the platinum tip and consequently had a gap of over .080". I installed NGK Iridium plugs and it idles like new again.
the delco plats often "lose the tips", I've seen (back in '01~) as many as 1 in 8 "bad out of the box", overall good plugs but, w/ tough installation on many cars, "doing it twice" isn't worth it, some shops swear by the Bosch +4 on GM engines, others say the heat ranges are "too generic", I guess the new Iradium's are "the best" for longevity and daily drivers, even still 60K would be my max interval....
To answer the original question, AC Delco is a brand name of Delphi Automotive, the parts company spun off of GM. They make much of their own stuff, especially the OE parts, but they do farm out a lot of parts as well. It's been established, for example, that many of their aftermarket oil filters are made by Champion, while the ones you buy at the dealer and some auto parts stores are made by Delphi. I'm not surprised to hear that the Iridiums are NGK. I would expect their platinums to be made in house, though, as I've never seen a spark plug with that kind of tip before.
The factory platinums on our '01 GTP are just plain NGK, not even an AC-Delco name on them. They are the laser platinum, ptr4b-15. Supposedly they don't even make a lot of the ac plats any more. The original AC plat, 41-921 for the 3.8 is replaced with 41-101, an iridium plug made by NGK. Its not fine wire like the IX though.
I am going to be trying the tr55 NGK in the GTP this week. If they don't last long I will try the tr55ix. Both are a little cooler plug than stock. Supposedly copper conducts heat better, so I'd think it'd be a little more resistant to pre-ignition. But the iridium is supposed to require less voltage...
I am going to be trying the tr55 NGK in the GTP this week. If they don't last long I will try the tr55ix. Both are a little cooler plug than stock. Supposedly copper conducts heat better, so I'd think it'd be a little more resistant to pre-ignition. But the iridium is supposed to require less voltage...
I just replaced the plugs in my Montana with the AC Delco Platinums that I bought from the dealer. I know some of the newer 3.4L are coming with the Iridium plugs. I haven't heard anything good about Bosch plugs in any vehicle.
Why are you changing them out at such low miles (70000Km ~= 43000 miles)? They are supposed to be good to 100,000 miles. I changed mine at 90000 miles and they still looked pretty good.
Why are you changing them out at such low miles (70000Km ~= 43000 miles)? They are supposed to be good to 100,000 miles. I changed mine at 90000 miles and they still looked pretty good.
somebody (not me
) needs to get a good spark plug book w/ cross references and heat range charts and see IF the Bosch (especially the +4's) are perhaps stretched by same part number being used over too wide a heat range...?? Maybe that's why they work well on some applications (the heat range is right on), but, in others the part # corresponds to a couple heat ranges more/less..?? My thoughts...anywaym, no problems on my LT-1 but, w 3K miles in 2+ years and new wires too on a 10K motor, that's not a good test..the delco's didn't look like 6K plugs (looked worse) when I changed 'em FWIW...
hey, inputs on my ponitac 400 engine thread please!
I'm changing them at 70,000km because to me they do not look good anymore.I took one out and it had a gap near .080". I know GM says there good for 160,000km but why wait that long? Anyway I will be using Ac Delco's or NGK's. Thanks everyone for the reply's
I replaced mine at 50K with Bosh Platniums. It idled rough, missed, ect. Even died on me a couple times.
I went to the dealer, paid $28 for 4 Delco Platniums. Put them in and they've been in there for 35K and run great. I'll probably leave them in for at least 25K more.
I'll never even THINK useing anything else again.
I went to the dealer, paid $28 for 4 Delco Platniums. Put them in and they've been in there for 35K and run great. I'll probably leave them in for at least 25K more.
I'll never even THINK useing anything else again.
I'll bet they had a supply problem with the Delphi AC Delco branded plugs and needed to get something quick, so they got a bunch of the equivalent NGK plugs. It's probably the same as the AC 41-921, especially when I look at the description on ngk.com. They certainly aren't cheap, though.
I would also be interested in seeing heat range information on various plugs. How do you find or figure that out?
I think it is because they switched to Iridium plugs, and AC didn't make Iridium plugs. It was easier and cheaper to source them from NGK is my guess. I think the AC platinum plugs are very good plugs, at least for the GM engines that I have owned.
Matt, NGK heat ranges go colder the higher the number. That is how I know the tr55 are colder than ptr4b-15. tr55 is same heat range as tr5, the tr55 is wide gap version. that is what you would want.
As far as Ac Delco heat ranges, they don't appear to have any relationship to the part number. Luckily some have done their homework. 41-932 is the next coldest plug from 41-921. Not sure that they make them anymore though?
Check out:
http://www.clubgp.com/newforum/tm.a...=41-921&language=single&tmode=&smode=&s=#8543
As far as Ac Delco heat ranges, they don't appear to have any relationship to the part number. Luckily some have done their homework. 41-932 is the next coldest plug from 41-921. Not sure that they make them anymore though?
Check out:
http://www.clubgp.com/newforum/tm.a...=41-921&language=single&tmode=&smode=&s=#8543
I've been running Autolite Platinum Pros for years now in everything. Functionally, they are identical to the AC double plats. Only problem I've seen is they tend to run a bit hotter than the eq. AC, so I pick the next heat range down.
Vader, what would that lower temp Motorcraft pn be for a 94-96 LT1 5.7 engine? What is the cost compared to a double platinum AC?
I also had the factory Delco plugs with gaps of over .080 with only 50K when I changed them on my Grand Am. I installed Autolite double platniums in my Dad's truck, and with 60K on them, the tips never fell of like the Delcos, and they maintained their gap to within .005. Just some food for thought if your looking for long lasting platnium plugs. Just put a lot of anti-sieze on them if you plan on leaving them in for their "stated" longevety, cause the factory GM plugs are a PITA to get out if they are really old and have been in since new.
APP106
Just make sure they give you the nickle plated ones. The blues steel ones don't last as well, but have the same PN.
$3.99 each vs $5.99
Actually GM retained the rights to the brand name AC Delco.
Delphi does manufacture many of the parts branded AC Delco. However GM is using many more suppliers than in the old days, thus other suppliers making parts for GM under the AC Delco name. Also Delphi is selling to many more OEMs other than GM than in the old days - in particular Toyota.
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