I finally removed the stock plugs. They are NGK PTR 4B-15.
What would you guys recommend I switch to based on my current mods with headers and an off road pipe :?:
41-932 were recommended by dbtk2 as one heat range cooler but they are factory plugs and cost $15. each from the dealer.

Are platinums no good for the series 1 NA? Ever since I put Bosh platinums in it likes to missfire. It had original plugs before hand at 98000mi. and ran better than with the Bosch plugs. However, I was warned on here that 3800s don't like Bosch items.

I have decided to go with NGK TR6 IX. They are Iridium plugs that are two ranges cooler.

my 3.8L (aka pre-3800...) of my '87 bonne is running on Champion plugs, they were installed by a popular chain'* local franchise way back when i didn't no anything about cars (about a year and a half ago... i had just gotten my first and still only car.. the '87!) anyways i have NO problems with misfires, etc. I personally would go with the AC Delco equivalent of my OEM plugs for now since I haven't done anything major to her yet.
Mike D

Well, I bought the plugs today but decided after closer inspection of my original NGK plugs and heeding the advise of Will to just go with one range cooler, so I have the NGK TR55 IX iridium plugs.

I can get them at Autozone for like $5 a plug or something like that. $15 each is rediculous. I would definately not go more than 2 ranges colder with your setup, especially since, as you have said in the past, most of the time you drive the car it never even has a chance to warm up. 1 range colder was a good choice, and was exactly what I would've chosen. Let me know how the Iridiums work for you. I haven't heard anything about them from L67 owners, so I would like to know what you think after you have used them for a few months or so.

Shawn

The GM dealer here is monopolizing a captive market. I bought the TR55 iridiums at Canadian Tire.....like an Auto Zone.....for $10 ea, that'* about $7 US.

I doubt that I will be able to tell how they are really performing until I pull them out for an inspection which may not be until next winter...unless I suspect a problem, like misfiring. I don't have an Auto Tap....yet, so I have to rely on guys like you to guide me along until I do.
Thanks for all your help.
I can hardly wait to fire her up after the headers are installed.

I use to run AC Delco Platinums in my Series I w/o any ill effects.....in fact, it helped it greatly!

What differences did you notice?

1 Billion Horsepower.

It'* friday and I'm in a humourous mood.