Whats the best spark plug?

[04SS99Denali]

stick with OEM ac delcos imo. ive changed my spark plugs in my NBS to NGK TR55 iridiums and i havnt seen even .1 mpg increase in the DTC

 

[Glock 22]

So for a 99' Tahoe 5.7L. What is the "Correct" gap for the use of NGK G-Power plugs?

 

[mgiroua]

Last year I bought some AC plugs for my Uplander and when I opened the box, they were actually NGK plugs with an AC number added. So, I bought NGK at half the price for my Yukon and they work fine. I'll second MrSmooth1031. Just my 5 cents.

 

[SunlitComet]

0.060 for L31 GEN-1 engines. Platinums are pre-gapped.

 

[yukon2004]

stick with OEM ac delcos imo. ive changed my spark plugs in my NBS to NGK TR55 iridiums and i havnt seen even .1 mpg increase in the DTC

What about any noticeable power gains?

 

[LI99HOE]

I installed Ac Delco 41-993's gapped @ .060. Originally did this one month ago and installed new AC Delco wires, cap, and rotor at the same time. After doing this I got the infamous P0306 code popping up occasionally under load/up hills.
Yesterday I pulled all the plugs, rechecked the gaps. Only one was gapped too far. I had a couple of the OEM spark plug wires come out of the boots...so I changed them with Bosch wires. I inspected the cap/rotor, and found that all of the terminals on the cap were corroded. Changed cap/rotor with Duralast Gold parts(brass terminals), and now the truck starts/idles/accelerates great.
Fingers crossed, but no code P0306...

 

[TTZ06]

Unless you are spraying or boosted, OEM plugs are all you would ever need.

 

[LI99HOE]

Very true TTZ06...... my point is..... beware OEM caps/rotor, and wires. That tune-up you just completed with them might actually be a tune-down

 

[99Yuk]

Very true TTZ06...... my point is..... beware OEM caps/rotor, and wires. That tune-up you just completed with them might actually be a tune-down

Actually it's not just OEM caps and rotors. I recently just did a 'tune down' when I installed my new MSD cap and rotor. They didn't make it a month before they had to be swapped out for AC Delco cap and rotor.

And worse, there's no way to tell before you install them...

 

[LI99HOE]

Wow 99Yuk.... I wouldn't have expected an MSD set to go bad so fast, especially since they offer brass terminals(and are a pretty penny).

Anyone ever try putting a bead of silicone grease or such where the cap meets up with the metal on the distributor, to prevent moisture from entering the cap, and destroying the contacts?