anyone run iridium plugs in their 4.0 hear alot of people saying about predetonation kinda has me worried

 

Did you do a search of this site yet? Do one and you'll find more information on this topic than you can read in a day.

Today is a full moon, literally. And if I didn't already know that, there's plenty of evidence on this site with the start of two threads concerning the most dreaded topics...... Oil and spark plugs.

Let the debates rage on!

 

I do, but because iridium tends to be hotter which can lead to pre-detonation and because it is less conductive than copper, I've done more than simply switch to iridium. And I may switch back to copper in the future anyway.

I have iridium plugs gapped to 0.050" with Magnecore 8.5mm wires, an MSD coil, and a full batt cable kit from 5-90 (Kelley's Work in Progress).

I might go back to copper 0.040-0.045" gap. Still thinking about it. I haven't had detonation issues, but I also am wondering if I'll be likely to develops them eventually and if it's worth the risk.

 

I've ran iridium for awhile but found it to be of no gain in the XJ. I'm my experience good old standard cheap to medium grade spark plugs work the best.