I have a 2010 GMC Sierra K1500 LC9 Flex Fuel OEM AC Delco 41-110 plugs. The factory plugs are gapped at .37. What should I gap the NGK Iridium's to their website shows .40 but factory gap is closer. I have EFILive AutoCal tuned by Black Bear Performance, K&N 63 Series Intake. What do you recommend for the gap of the plugs? I drive the vehicle very hard and it will be tracked.

 

I'd think that you'd want the factory gap on either, as NGK's are often factory equipment, and/or the Delco's are often repackaged NGK's. You really shouldn't have to touch an iridium plug as they usually come pre-gapped since they're so easy to break. You don't want to pry against the iridium tip as it will surely snap off...if you must gap the plug, adjust the ground with needle nose.

Curious why you're changing the plugs on a 2010, you hit 110k already? Iridium plugs go for many, many miles...

 

Ive gapped all my LS base and BB496 GM motors at .35"

 

I never pry against the tip of the spark plug unless its a cheap copper plug. I use regular pliers to grip the tip to open the gap up, I went with the OE Laser Iridium Plugs gaped at .038 most were are that there were two closer so I used pliers to open the gap up. The book shows .040 but all the factory plugs were gaped at .038.