I currently have about 4,000 miles on my new engine and these spark plugs. I have a ZZ4 equivalent with all the specs in my signature. I am running a slightly higher compression ratio then a stock ZZ4, my engine is about 10.3:1 compression ratio. I was having big knock problems even with the stock timing tables (I have made my own custom chip).

I have read many bad things about bosch spark plugs so I decided to pull the plugs and put some AC Delco stock corvette plugs in (FR5LS), which I haven’t been able to try out yet, to see if that will solve my knock problems. When I pulled the plugs I was surprised at how off color they are. What does this red color mean? Are they getting to hot? Do I need to go to a cooler plug temperature. The bosch plugs I pulled out have the part number FR8DPX written on them and I can not find there heat rating anywhere online.

Here is a picture of my spark plug, can someone tell me what red color means?

 

check these out....

http://members.uia.net/pkelley2/sparkplugreading.html
http://www.nightrider.com/biketech/spkplghnbook.htm
http://www.hioutput.com/tech/plug.html

 

Is that pic a good repersentation of the real colour? A nice tan colour is good.

I'd chuck the plat plugs and go back to copper. Plugs need to be pulled everynow and then and read. Plat. is meant to stay in there too long and can freeze right into the treads.

Even on my LS1 when it was brand new, I pulled the plat plugs and threw in a set of copper NGK's.

Antisiieze on the threads of course and dielectric in the boots. I"ve been doing that for years too.