Here are the plugs from my 383 LT1 ... Pulled them after I've been noticing a Spark knocking type noise under medium to full throttle over the past few months or so ...

I originally thought that I was getting bad gas which was causing the issue, but it continued ...

Pulled the plugs and changed them ... haven't done any measurable driving since the plug swap ...

Here they are ... Doesn't this red like color usually mean something to do with the fuel? I've always ran 93 octane through the 383 ... and from various stations ...

 

Second pic down, the one on the left, is that insulator cracked? Also are those oily deposits on the shell? How many miles on those plugs?

 

Appears to be cracked ... Yes, some oil deposits ...

Plugs have 8 or 9,000 miles on them ...

 

never seen red before. sure you aint got rust in the tank? rich would be black, coolant would be white and chunky, and lean ofcourse would look new.

 

About 3 months back when I first noticed the spark knock type sound, I added a bottle of octane booster just to see if it helped ... I've been told on another board that that is what would cause the red ...

I've sinced changed the opti and the plug wires all look good (MSD) ... now, new plugs ... I'll drive it for a while and see if I continue to notice these issues ... if so, I may have to run it on a dyno and see if we can pin point the problem at all ...

 

Also, it's hard to tell from the pics but you want to look at those up close under a higher magnification to see if there are any little ***** of aluminum on the tips of the plugs - they usually look purplish on a light colored insulator, but if you see anything like that you might have had detonation. Oil in the cylinder could cause it, the cracked insulator, of course, could cause misfiring.

 

just an FYI, chevron supreme with techron turns the plugs that rusty color. mine go rusty color also on pump gas, as thats all i run.

 

Red to purple deposits on one side of the core nose are an indication of a fuel additive. While many of these deposits are non-conductive and do not contribute to lack of performance, some fuel additives contain octane boosters that leave conductive deposits on the core nose. Care should be taken to select fuel additives which are compatible with ignition systems and do not contain conductive materials such as octane boosters.