I have a LQ4 motor bored/stroked to 408 cid. I also just changed cams from an LS1-GT2-3 to a Comp Cams G3 XFI 266 HR15. When I pulled the spark plugs, they were absolutely burned up! NGK Irridium's that were only in the truck for a few thousand miles. The truck ran but the tune has never been quite right. Have been working with the tuner on this for a couple of years now. I finally decided that the GT2 cam was killing this motor. Did some research and settled on the Comp Cam. I know the tune was way rich, and the pistons are covered with carbon. The motor only has a total of less than 8k miles since it was built.

So the question...I didn't want to put in another $10 spark plug and just burn it up, so I bought Denso Platinum TT plugs so I can get this thing tuned, and will upgrade plugs later. After much searching and thread reading, I haven't found any definitive answer for spark plug gap on a built motor...except for the irridium's. What gap should be used on a 408 stroker motor, N/A, with platinum plugs. Should I use the stock 6.0L gap the plugs are factory set to? I would assume that there is a fine science to plug gap when you take into consideration all of the engines internal dimensions, tune and intended use, etc. Where does one begin? My burned plugs currently in use are killing the tune and the truck runs, but when you give it some gas it's like a drunken ***** (get a mental image of that!)

 

Although your description is entertaining it doesnt provide much useful information...do you have a picture of the spark plug? Black would mean too much fuel, but when you say burned that makes me think it didnt even enough fuel and might have too much timing as well. A picture would be easier to diagnose.

If you arent spraying or boosting stock gap should be fine.

 

First of all you need to get the tune on lock down so you don't run into the same problem or damage the motor. Also, like Atomic was saying a pic can help diagnose mostly what your asking. Another thing is junk the iridium spark plugs... Run stock gap on your plug or you could probably gap a lil less... NGK is a really good brand and what I run in my truck...

 

Sounds like the tune needs to be dialed in rather than it being a mechanical issue.