I bought my Z a few owners after it was TT'd. It has always had a slightly rough idle, and had a hot start issue, where it dies after starting when its warm and I need to blip the throttle till it levels out.

I know the engine is built, and it has 550s and a Utec, running an APS TT kit @ 16psi.

I have lfr7iax-11 plugs in it, but I wanted copper plugs but could only find lfr6a-11 plugs. So, I put a set in for about 200 miles, but I noticed my EGTs went up about 100*-200* higher just driving normally, it ran better but I decided to pull the plugs.

So, I've decided to ask the forum experts here some opinions on how the plugs look. And if I'm safe using the 6a's or should keep with the 7aix's?

The first picture is the 7aix, and the second is the Cleanest/dirtiest 6a

 

the 6's are already 1 step colder than stock. YOu dont need 2 steps colder with the 7's with your basic build.

there are no copper 7 plugs, so thats why you coudlnt find them.

 

You have 2 steps cooler. For your setup lfr6's should be fine.

 

that's good to hear. I was worried about burning a hole is a piston or melting a plug.

thnx for the replies

 

Looks to be running a bit lean in the right pic

 

it might be the camera pic but it looks like the first pic (on the left) has specs all over the porcelain which appears to be detonation. Again, hard to tell from a pic but dark specs on a plug is a sign of detonation.

i'm with the rest, you don't need 2 step colder. I'm running 1 step colder for mid 500hp pumpgas and i'll be pushing it much further on e85 and not worried about only running 6's.

 

the first spark plug pic is a plug that was sitting in my garage for a couple of months, thats why it's got some crap on it.

 

No detonation signs on either plug. Put the coppers at 28thou and be happy.

 

update:
Car is running a lot smother, it's got more low rpm grunt which is nice to have zooming through the city. And at full throttle, my EGTs are the same as the colder plugs, so I'm not worried about them anymore.

Thanks for the input.