Slp2002Z28

whats the correct gap for the spark plugs..05 gmc 5.3??

03 BLACKOUTSSS

iTrader: (3)

I believe they are factory platinums, so I think it should be .040"

Slp2002Z28

I put ngk tr 55 gap-out the box

viciousknid

iTrader: (8)

i think it depends on the plug.

what kind is it?

skolman91

iTrader: (28)

i just did mine recently and checked them outta the box and they were all around .055 so i didnt mess with them. imo i wouldnt go under .045

terravast4

iTrader: (25)

specs call for 2004 and up .040 gap

budhayes3

iTrader: (19)

That's the factory gap for an iridium plug. If running copper or platinum, they will work best gapped around .055-.060

BlackGMC

iTrader: (31)

That is what i just gapped mine at when i recently replaced them...

For the experiences on my 04, i don't agreee with that...

I have tried tr55s gapped at .60, .55, and .4.. The .4 idled the best but not as well as the iradiums.....
on the Iradiums i just put in they idled best at .4...

budhayes3

iTrader: (19)

That's interesting, you should *generally* idle smoother with the wider gap I believe. Iridiums pretty much have tighter gaps than copper or platinum, there's a precise reason for this which I used to know when I spent a lot of time researching spark plugs, but I'm drawing a mental block on it right now for some reason. My truck came factory with platinum plugs and the spec is .060, but fwiw, when I removed my plugs the gaps were inconsistent and ranging from .045 to .065, and the truck ran fine. I swapped in some pre-gapped Denso Iridiums, and then tried some NGK TR55's gapped at .055, and haven't noticed any idle differences, and I'm pretty keen to how my truck runs. Although, there may be differences in the tune from an 04+...I think someone (might have been you actually?) posted up slight spark dwell differences.

GMCtrk

iTrader: (27)

I run tr55s @ .055". Works fine.