Ok, someone has to set me right. I have AC Delco plugs in my BWR heads. The plug number is 41-630. Now I know the 630 number is the important part. A member that knows his way around suggests I run a colder plug, one step colder to start. I have been all over the AC Delco web sites and am now more confused than ever. I don't even know how I ended up with the plugs I have now! HELP!