: Regapping platinum plugs & best NA performance gap



stngh8r
08-26-08, 12:37 PM
-June: Installed new AC 41-950 plugs gapped .50 and MSD wires. Car ran better, smoother, started better, etc.

-July: A coil pack bit the dirt. All the coil packs were replaced with Accel coil packs. No real change from before, but performance was par or better.

-Today: While R&R'ing the EGR valve and cleaning it, I was leaned up on the hood of the car when I noticed the GM engine information sticker on the hood states .60 spark plug gap! Well, with the new coils, I was kinda curious if I could push the spark plug gap open a little farther anyway and now I see this sticker and wonder where I come up with .50?? The reason I came up with .50, is because that is what the Haynes manual called for! So which is correct? .50 or .60!? My thought process is that GM is more likely to be the expert on the engine recommendations since their the ones that built it. But maybe Haynes knows something that could have changed since that sticker was printed??

Being already curious about running a .60 gap regardless, seeing this sticker only fueled my desire to yank them out and go from .50 to .60, so that the plugs would be "most" correct. So I did.

Questions:

1. What is the best or recommended NA performance gap?

2. Did I screw up by regapping platinum plugs that have been fired?

Submariner409
08-26-08, 01:04 PM
stngh8tr, Check your owner's manual for plug gaps also. Maybe someone in here has a '97 Factory manual.........I have the different coil packs, and my '02 hood sticker calls for .050".

Heck, call ACCEL and see if you can hook up with one of their techs.....they specified the windings, they should know their recommended gaps.

(For someone used to standard ignition .030 and .035, .060" looks like a mile !)

Those platinum pads on the ground electrode don't like being bent, but if you only bent the electrode at the curve where it's spot welded to the shell you're OK. My thinking on the gap is that a .050" is pretty large, and would tend to create a somewhat hotter spark that would have less tendency to "blow out" in a turbulent chamber (high rpm).

AJxtcman
08-26-08, 02:15 PM
This is the impression I got from GM.
Platinum & Iridium Plugs are not to have the gaps changed. If you get a plug that is out of spec for the gap out of a set you are to get another one.


The gap on these types of plugs must be square. That is the reason that you are not allow to gap them. I guess a couple of thousands would be ok, but that shouldn't cause a durability issue any way.
http://i224.photobucket.com/albums/dd25/AJxtcman/Ignition%20systems/pic_platinum.jpg

If the car calls for a .065 gap and you get a replacement plug with a .050 gap they are to be installed at .050

If you were using a AC-Delco replacement plug in a case like this. The replacement plug has a revised gap and you need to keep it that way.

stngh8r
08-26-08, 03:30 PM
So should I regap them again back to .50? Or leave them alone? I agree with sub that .60 sounds like alot, but thats what was posted on the hood and I was under the impression with plug gap theory, the bigger the better as long as there is no detonation.

best I can recall AJ, these were pretty close to .50 when they came out of the box, but not quite.

I just hope I haven't messed up with these high dollar plugs. I guess I should have asked before I started regapping. grrr..

Thanks

Eric

Ranger
08-26-08, 04:32 PM
I do remember a discrepancy, but .050 is correct as I recall. I'd put them back to .050

Submariner409
08-26-08, 05:01 PM
eric.......Those plugs are $4.92 ea. in 8-packs from RockAuto.

............If the car is running OK with no hesitation, no rough idle, or miss at WOT redline, don't mess with it any more.......my .02

tateos
08-26-08, 05:15 PM
eric.......Those plugs are $4.92 ea. in 8-packs from RockAuto.

............If the car is running OK with no hesitation, no rough idle, or miss at WOT redline, don't mess with it any more.......my .02

I agree with Sub on this one - 10 thousandths is not going to make that much difference