AC Delco Iridium Spark plug gap...
Pro
Joined: Aug 2009
Posts: 662
Likes: 0
From: Loxahatchee FL
I tried .050 today ran pretty good but increased KR by 2.0 at WOT 3800-6300 rpm, took it back to .040 and KR was gone, now im trying .045 as i can always reduce timing at WOT above 6000 and 100 MAP kpa.
Plugs came out and looked great at both, nice white porcelain..
Plugs came out and looked great at both, nice white porcelain..
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
Don't know if it's true, but I heard one reason they went from a 0.060" to 0.040" gap was to not work the coils so hard. I think the Tech Dept at NGK mentioned that. The larger the gap, the harder the coils have to work (and run hotter as a result) until they can't make a strong enough spark to jump the gap.
Tech Contributor
Joined: May 2008
Posts: 3,100
Likes: 17
From: Somers, CT and Clermont, FL
St. Jude Donor '09-'10-'11-'12-'13-'14-'15-'16
Don't know if it's true, but I heard one reason they went from a 0.060" to 0.040" gap was to not work the coils so hard. I think the Tech Dept at NGK mentioned that. The larger the gap, the harder the coils have to work (and run hotter as a result) until they can't make a strong enough spark to jump the gap.
Most likely, the reason for the reduction of spark plug gap, to 040 from .060, was to reduce misfires, which results in lower emissions.
