fullcircle

I installed Scorpion 1.8 roller rockers and valve springs on my 99 WS6. At the same time i wanted to change the plugs. I ordered a set of Delco Iridium plugs from the dealer by telling them what car I had. I was surprised that the plugs in my car which have never been changed were factory NGK Iridium plugs. When the Delco Iridium plugs showed up they were gapped at .040. Now the owners manual says to gap them at .060. When I gapped the plug the electrode arm was bent back so far it didnt have a good spark path anymore. What gives? I sent them back. Are the NGK Iridium plugs pre gapped any bigger?

sroach20

iTrader: (31)

it said .060 from the factory, they changed it cause they found out it did better at .040. never gap a platinum plug, ever. they are preset and you can damage them easily by trying to gap.

hammerhead

iTrader: (1)

I didn't think GM used NGK from the factory. Are you the original owner?
I just replaced the OEM ACDs at about 70K with ACD iridiums and they were pregapped. The old OEM ones were still pretty clean.

fullcircle

I bought my car from the original owner and it had 4500 miles. Its a 30 th anniversary T/A. He never registered the car. So I am pretty sure the plugs werent changed. My thought is that maybe the WS6 cars had NGK plugs?

staringback05

iTrader: (8)

to my knowledge gm never used ngk....they have always used ac delco....as stated before if they come pre-gapped leave them alone

Grimes

iTrader: (3)

some cars did come with ngk's from the factory, my friend's car did. i dont know if they were iridium though.

staringback05

iTrader: (8)

thats odd then....93-02 gm used ac delco

WayneSS01

I ordered my car from a local dealer. It came with Denso plugs. Changed to A/C Delco Iridiums last year. The A/C Delco site said not to deviate from the pre-set gap.