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yellow plugs?

633 Views 12 Replies 8 Participants Last post by  Masssilversrt4
I pulled my plugs today to change them and they are yellow like butter:jester: could the coloring be from c-16 race gas or is it time for a colder plug?
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mmmmmmm, butttterrrrr :druel:
Glazing appears as a yellowish, varnish-like color. This condition indicates that spark plug temperatures have risen suddenly during a hard, fast acceleration period. As a result, normal combustion deposits do not have an opportunity to "fluff-off" as they normally do. Instead, they melt to form a conductive coating and misfire will occur.
too hot of a plug, need 1 or 2 steps colder. :)
Could be incorrect fuel mixture causing the plugs to glaze, shorting them out during a run resulting in sudden heat fatigue. Fuel additives will also discolor plugs, but I've never seen yellow. VP "C" series fuel will show as a light gray. Torco will show as a redish/orange brown.

Good tech article on reading plugs.
car ran fine no misfire etc.. plugs looked good besides being yellow, afr are in check. guess i'll try a colder plug:thumbsup:
Only choice for colder plugs are iridiums? whats up with that?
If you run leaded race gas that will do it. Mine are always yellowish after running race gas.
addictedtosin said:
If you run leaded race gas that will do it. Mine are always yellowish after running race gas.
I run nothing but a 50/50 mix c16/streetblaze 103... before I started to run race gas my plugs "always" looked good.. I will be turning the boost up soon so I will need a colder plug, I just don't want to run the ngk iridiums cause my car ran like total shit the last time i had a set in with various diff gaps... are the denso any better?anyone know of a non iridium colder plug?
4306 Ngk..
Masssilversrt4 said:
4306 Ngk..
Thats all I run:thumbsup: but if it's a heat issue and have to colder I want to stay away from iridiums but as it looks thats the only colder plug besides denso! from what I have been told and my informer could be wrong the ngk iridiums 1 step colder are pretty close to stock heat range if not hotter.. someone needs to make ngk make a 4306 in a colder ranges!!!
Never had a problem with my 4306's on my built motor with big turbo/cams etc..
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