I got the NGK's...I asked about the diamond cuz of an episode of either horsepower tv or extreme 4x4 that was on the powerblock that tested them out on a motor and they said it was like a 10-12hp gain with them but I was kinda skeptic

 

I love watching those shows on a saturday morning but they really are just cool paid ads. Still beats reality TV lol.

 

I'm always skeptical about horsepower gains from just plugs...the way I see it that's only gonna happen if there was a problem. If there was a power increase I'd guess it would only be at a narrow rpm range...

 

I took the NGKs back and got the AC Delco but ended up not needing them anyways cuz the ones that were in it were still like new. My dad has a 96 vortec 5.7 and he put Bosh in it and it ran like crap so he put Delco back in it and it ran like a champ even with 210,000 miles

 

delco, ngk, autolite are what seems to work well in gm vehicles. Oh, and as to the "miracle" plugs, you ever hear of the pulstar plug. they claim it amplifies the coils output to send out a million volt spark, or 20,000 times more energy output than a conventional plug... and claiming a pulsing fire so more than one spark(without a multi-spark discharge equipped system) but after the math, you theoretically can get a million volt spark, at about .002 seconds before your supposed to, and a duration of about .03 seconds if i remember, or something like that. but thats with a 100,000v coil but you would require more amps than your battery outputs so me and my buddy debunked it in 10 minutes with a calculator... yet they want 113 bucks for a set of 8 plugs... ill stick to NGk...

 

i know this is an old thread, but have am i the only one that has pulled my delco plugs and seen that it says ngk on one side and ac delco on the other? new 5 miles silverado back in 04 and thats what was written on them.

 

Never seen that before,my 2004 had delcos all around.

 

yea... also seen NGK plugs in a stock Gm.. and also ACD's in others..

ive only seen the NGK ACdelco one time.
but GM buys them on bids i believe. which ever they accept is what they use, and there was a short peroid where they used only NGK's