What's the difference between Autolite 104 and 106 sparkplugs?

 

104 is 1 heat range colder.

 

yep, the 104's are colder. I would suggets gapping them at .035 or so instead of the factory gap.

Lloyd

 

What does the colder plug do for you? All the parts places say to use 106 stock. I have your LE2 heads and you said to use the colder plug. So why do I want to use the colder plug? I'm also using the thinner gaskets too.

 

Colder plug resists detonation more on high compression engines and gapping them less is so you don't blow out the spark and you get a stronger spark for your application.

 

The only difference is the temperature of the plug at the electrodes. Too hot, and the electrodes burn, too cold and the plug fouls. Higher compression/higher volumetric efficiency requires a colder plug to conduct the heat from the higher combustion temperatures, and keep the electrodes from burning. In an extreme case, too hot a plug can turn into a glow plug and cause pre-ignition, which can damage the pistons and heads, among other things. A stock engine needs stock heat range plugs.

 

106s from my experience are slightly hotter than a stock delco platinum. I was running 104s at a .04 gap prior to nitrous, and now I'm running a 103 at .035. I love autolite plugs BTW!