Copied from another forum. This bulletin is being revised to bring attention to the Set Gap Per Vehicle Specification on the ACDelco® Iridium Spark Plug Boxes. Please discard Corporate Bulletin Number 03-06-04-060 (Section 06 -- Engine/Propulsion System).

• A new spark plug has been released for use in the above vehicles. The new spark plug has an Iridium tip instead of the current Platinum tip. Due to the different tip design, the gap of the spark plug has also changed.
• The new spark plug, P/N 12571164 with AC Delco P/N 41-985, is gapped to 1.01 mm (0.040 in) when the spark plug is made.
Notice: The spark plug gap is set during manufacturing and should not be changed or damage to the spark plug may result. Any new spark plug found to not be properly gaped should not be used.

 

First I've heard of this. I've always gapped my plugs at .060 yet don't recall which plugs I put in last time. Maybe I need to pull one or two to see how they look.

 

All iridium plugs will be gapped to the application by the manufacturer. The fine wire design makes it VERY difficult to properly gap the plugs as the center electrode can be bent or broken if improperly handled.

This is the first I have heard that the gap dropped for these plugs though.