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I need to get these numbers straight tonight or no racing for me tomorrow.
I have 2 crack spark plugs. So changing them out.
Heres the problem the ones pulled out are AC Delco 41-931 (25162487)
The ones I got from GM are AC Delco 41-985 (12571164)
I also have some NGK TR55 (3951) from autozone.
The two new ones I got do not match the old ones from the car. The bottom of the plug by the electrode is almost 1/8 bigger on the two new ones than the one from the car.
Which is the right one. HELP...