Mopar Muscle Association UK

I have the same plugs in my motor!

Got mine off Dave Billadeau, so should be ok!!

Those plugs are too cold & will load up , normal use for those plugs would be high compression motors or mild nitrous/blown use , NGK 6 would be better.

I run NGK 6's in my cars - seem to work well all around, even the higher performance stuff. Never had one go off yet... famous last words...

Good point guys!

Any idea what compression you're running with those eddy heads?

Different engine combos will require different plugs , you can have two identicle engines (hypotheticle spelling) that will show different plug readings dependant on the tune up , if one set of plugs from engine 'A' shows it requires a colder plug as opposed to engine 'B' then obviously engine 'A' is in need of a better tune , i run NGK 6 on the 605" with 9.5 CR , although i could get away with #5s dependant on weather conditions , if the engine runs lean , too much spark lead , runs hot , incorrect fuel , then the plug will show a colder one would fair better , but this is'nt always the case , just a band aid , when i run the nitrous i use an NGK -8 , when i eventually step up i will use an even colder plug..........too hot a plug can cause preignition/run on/detonation , so it's pretty important the correct plug is used for the application , this is the reason plug reading is important as it will tell you what the motor wants , you could say it's the next best thing to a chrystal ball.

If ever in doubt always go for the colder plug.

I was running 12.3:1 on the Indy heads with 6's in; so a fair range of CR.