What is the difference between hot and cold plugs (besides one is hotter/colder than the other) and what are the benefeits/ drawbacks of each one. Also, what do the spark plug numbers mean, for example, would an Autolite 23 be hotter or colder than an Autolite 13?

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66 Big-Block Chevelle Houston, TX ACES#3321

Heat range refers to the length of the insulator. In the simplest terms the shortest path for heat transfer to the head and coolant is the coolest plug. Too cool = deposits and miss-firing. Too hot = melted electrodes, preignition etc. The best plug is just hot enough to stay clean given your engine combo and driving habits.

Check out this link for all you want to know about plugs...MK
www.acdelco.com/parts/sp_ident_set.htm (http://www.acdelco.com/parts/sp_ident_set.htm)

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hometown.aol.com/mkrauser/gmracing/gmracing.htm (http://hometown.aol.com/mkrauser/gmracing/gmracing.htm)


70 Chevelle Fathom Blue
70 Malibu Convertible Midnight Regatta Blue

Chicago - Suburbs



[This message has been edited by Mkrauser (edited 10-18-99).]

as for the autolite heat ranges they would be the same.

23 would be a different type of plug than a 13 but the heat range is specified by the last digit. In this case they are both 3. As i recall autolites numbers go up for hotter range so a 9 would be hotter than a 1.