Which NGK Spark Plug Do You Use In Your 440 on the Street?

Typo Hit the 5 instead of the 8.
Meant to say R5670-8 were too cold on the street only used R5670-5 or -6. Bob is correct heat range goes the other way. Used to Run Champion J10Y or J11Y on the street. R 5670-8 Were Like a J63Y if my memory still works..