16 replies to this topic

[mailman]

This is quite useful, I've wondered for a while what the actual reasoning was for the grading.

I have just changed to 6's from 7's as I (possibly quite mistakenly) thought that the increase in comp ration to 9.75:1 would require the colder plugs that are marketed as fast road. I was told to go for these by Minisport.

My 7's have been very sooty. My car is very likely running rich at some point but I haven't been able to get it properly checked yet. Would the 7's contribute to the sooty-ness?

[jaydee]

Try 6s, you need to be well above 10:1 to use 7s

Plugs get soot because dont get enough heat to clear off