Spark Plug heat range

[Snakebit]

How do you determine if you need to run a hotter or colder plug?

[Ron61]

One way is by your driving habits. If you do a lot of putting around town look at the plugs and see if they are fouling. If they are, then you need a hotter range. If they are a tan and clean, then you are ok.

Ron

[RICK LAKE]

Snakebit IMO the only real way to tell is by going to a dyno and running the car with new plugs and go up or down a heat range and see what the power readings are. The most important thing is the A/F readings and checking the EGT's on the header pipes. What's wrong with your car? Don't you go to english town for the car shows when the swap meets are there? LM-1 is a nice monitor for checking the motor when running. You want to see about 12.7-13.2 for A/F readings under WOT and about 13.3-13.5 under cruising. I am not a big fan in running lean. Some guys run in the 13.7- 13.9, IMO too lean. Check the timing also. My understanding is that webers don't need as much timing total as a carb. You would need to ask a PRO on this. A good dyno shop will do the same thing. Rick Lake

[mpanten]

They should look like a choclate color. Better to cold than to hot. My father used to own a service station in the 60's and 70's and told me stories about people who drove 99 percent of their time in town. Well as you can imagine, as with most cobras, engines were not computer controlled those days. The problem was that they kept fouling out plugs in town and would switch to a hotter plug. That worked fine unil they left detroit and hit the highway and got about 20 miles south of Toledo and melted a piston.

[wtm442]

http://www.dansmc.com/Spark_Plugs/Sp...s_catalog.html

[Rick Parker]

http://www.dragstuff.com/techarticle...ead-plugs.html