I am getting ready to put AC Delco Iridium plugs in my 98 LS-1. Do you go with the factory gap of .060" or do you do something different?

 

No!!! .040!!!!

 

They are pregaped don't mess with them! just check and if one is different take it back

 

It will run great at .040 !!

 

 

They come pre-gapped. Do not change them.

 

...and put a little anti-seize on the plug threads and Dielectric grease in the boots for easy removal next change

Chuck

 

Anyone know what the pre-gap is set to?

 

.040

 

.040 last time I checked, although .060 would work fine and give a smoother idle.
Problem is they can be broken easily trying to change the gap

 

GM is pretty emphatic about not changing the gap.

it never hurts to check the gaps before installation. it only takes seconds and you never know when you might find a plug that has been treated rudely

 

Interesting, the owners manual says "Spark Plug PTJ16R15 (0.060 inch Gap)"

.020 is fairly large difference for plug gap.

Are we certain that plug is pre-set to .040?

 

Her you go straight from GM
Subject: Information on New Spark Plugs and Gapping #03-06-04-060A - (02/12/2007)



Models: 2004 Buick Rainier

2002-2004 Cadillac Escalade, Escalade EXT

2003-2004 Cadillac Escalade ESV

2004 Cadillac CTS-V

1997-2004 Chevrolet Corvette

1998-2002 Chevrolet Camaro

1999-2004 Chevrolet Silverado

2000-2004 Chevrolet Suburban, Tahoe

2002-2004 Chevrolet Avalanche

2003-2004 Chevrolet Express, TrailBlazer

1999-2004 GMC Sierra

2000-2004 GMC Yukon, Yukon XL

2001-2004 GMC Yukon Denali, Yukon XL Denali

2002-2004 GMC Sierra Denali

2003-2004 GMC Envoy XL

1998-2002 Pontiac Firebird

2004 Pontiac GTO

2003-2004 HUMMER H2

with 4.8L, 5.3L, 5.7L or 6.0L V-8 Engine (VINs V, P, T, Z, G, S, N, U -- RPOs LR4, LM4, LM7, L59, LS1, LS6, LQ9, LQ4)

Attention: Please disregard the Set Gap Per Vehicle Specification statement on the side of an ACDelco® Iridium Spark Plug Box. The statement will be removed from the boxes in the future.


• 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 gapped should not be used.

 

Interesting but the way it was worded they sure left some reading between the lines and assumptions to be made. They say ignore the reference on the box and state what the factory gap of the plug is and not to change it. But they never said this is what is approved for use as is from the factory in these vehicles specifically Corvette.

They should have worded it such that it confirms the proper gap when using this plug is .040 and this is approved.

Usually these things are scrutinized by legal, wonder why they left it open ended?

 

it's a tech bullitin for dealers & AC Delco mechanics. so it's implicit

 

That explains why they make so many mistakes when working on your vehicle.

 

Yep too many assumptions

 

Just wanted to say thanks for all the responses. I've learned alot.

 

Ok I just ordered a set of these plugs, AC 41-985 and the part number on the plug is 12609877 NOT 12571164 as stated above...
WTF????
Do I leave these at the gap they're at now?
Are these a newer or older stock number GM is using?

 

part numbers change. Don't mess with them just check to make sure they are right and take back any that are not. for example if all are .040 and just one is .030 or .060 then take it back