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Upgrade Bosch plugs to Autolite ?


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So I felt like the Big Red Dog needed some TLC (after several years of only gas, oil, filters, tires and wind resistance).

Well, I also thought about the "chuggle" quirk with the tranny clutch locked-up at level-smooth 45-52 mph. This fine site suggested that it might be caused by a slight missfire under low load.

OK, then I guess I'll be nice to it...for at lest a couple hundred bucks.

I called the lube shop to ask about installing new plugs and the kid saz OK. He gets back to me with a quote of about $280. I asked if those were the original AC-Delco plugs and he saz, no these are an "upgraded" Autolite. I said no, go ahead and "downgrade" me to the original plugs and he said that would be extra cost ! :lol::angry:

I called the the GM dealer (who is really a good guy - he estimated the value on the BRD at $3,750 a few years ago, helped with buying and registration fees). They said about $200 for original AC-Delco platinum plugs. Plugs were about $8.00 each and labor about 2-hours. I'll bring it in Tuesday I said. They actually charged a buck less per plug and only 1.5 hours labor (total was $162). Yea I know, about $100 too much for you guys who like to wriggle arond the back side of the NorthStar. No thanks anymore, I'll just pay the money... ;)

I picked up the BRD today and after a couple blocks from the dealer, punched it up past 120-mph entering Interstate-80. It pulled strong all the way with nary a problem. We'll try it later on the flat, smooth road the the chuggle speed.

Oh yea,

The service kid brought out all 8-plugs and I took some pictures. I beleive these might have about 80,000-miles on them. Mostely high speed and virtually no stop and go traffic (10-minutes to work at 13-miles away). Pics below should link OK from the main page.


1 plug = www.geocities.com/tdkueper/p1010228

8 plugs = www.geocities.com/tdkueper/p1010224

They were Bosch Platinum r6762 hr8dpx. The gaps were about .060 with a round wire gauge. Some were a little lighter (no, I forgot to ask the mech to number them). All the gaps were relatively equal

They also said that the plug wires might need to be checked in a week or so in case any were cracked by the handling. Anybody have that experiance?

Ready for another 80,000 I guess :rolleyes:

Add power to leave problems behind. Most braking is just - poor planning.
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What was the original gap of those Bosch Plugs? From the erosion of the tips of the 'ground' electrodes, I'd say the gap has increased _substantially_ since they were installed. 4 of the 'ground' electrodes should exhibit significantly more wear than the other 4 because of the waste spark configuration, which is another reason the OEM plugs are desirable. Are the centre "platinum" electrodes all intact? Examine the tips of the ceramic 'cones' for missing or protruding cores.


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The original gap was 0.050 per the Bosch website

I cannot discern any differance in the gap between all 8-plugs.

All the side electrodes look identical in length, width and thickness.

There is a little dimple still present under the side electrode, opposite the cone tip. It is uniform and does not appear to be erosion-based.

All of the center electrode cone tips are perfectly intact and the electrode is flush with the cone tip. Some of the light tan coating appears to be off to one side

There is no dust or carbon what-so-ever between the center electrode and inside wall of the threaded steel body.

If I clean up the tan coating and a tiny bit of hard scale on one of the side electrodes, tap the side electrodes down 0.010 - they could probably be sold for new... ;)

I might check the mileage on the next 300-mile round trip tomorrow. We'll see if its still about 23-24 mpg at 80-mph true average. :)

ps, The tranny "chuggle" might be a bit less. <_< But then again I rarely drive on a level, smooth road between 45 and 55 mp anyway.

The BRD willl just have to wait another few years or complain about something a lot more significant - to get any more "tinkering time" and chit-chat with the new GM iron at the dealer. :D

Add power to leave problems behind. Most braking is just - poor planning.
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ps, The tranny "chuggle" might be a bit less.

Have the EGR feed passages been cleaned recently?

Here's a pair of 20,000 mile Bosch plugs from a 4 cylinder application. The side electrode on the righthand one is almost like new; the lefthand electrode shows considerable erosion. Some of your 80,000 mile plugs show significantly more wear in this area.

BTW, a couple of those plugs were missing the platinum electrode. Maybe you need to hit WOT more! LOL



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