I am curious if someone could explain why heat ranges play such a role when going Blown/N20 and N/A Motors.

My father in law has had a 63 Biscane (sp) with a 409 motor (N/A) and after extensive testing, he noticed that going with a plug that was about 5-6 heat ranges hotter than stock, really helped out in performance. I would like to know "Why does sometimes going with a hotter plug on a N/A motor help"
I was always told that its best to go 2 heat ranges colder on our cars (when blown) and it seems to work great, I know it helped others with pinging problems but what I really want to know is "HOW DOES GOING COLDER HELP" on Blown or N20 Motor.

Please explain in Full detail.

Inquiring Minds Want to know
Claude

 

The heat range only has 1 specific purpose. That is to make the plug tip hot enough to burn off deposits, while not getting so hot as to essentially glow & ignite the fuel without spark. This preignition can cause serious engine damage. Too cold & the plug can foul & cause misfire. If a stock engine needs a hotter plug, it is most likely to cover up an oil usage problem, or possibly a weak spark or very rich mixture. Chances are if your discussion was about a 409 Chevy it also had a point ignition & is a very weak spark in comparison to what is available in stock form today. Many times in the days before electronic ignitions a street driven car needed a few hard passes to "clean it out" before best performance was obtained due to this fact. Basically the more heat (read HP) in the cylinder due to combustion, the colder plug you can run. High compression usually needs a colder plug as does, nitrous or boost.

 

Is running a colder on a stock motor a good way to fight detonation?

I ran the TR55s for a while and when I pulled them they were white. I swapped to TR6s a few months ago. Checked them today and they were more of a rust color - seems like its helping a little...

EDIT: My car is completely NA.

Ryan

 

Thats interesting Ryan since I pulled my autolite 106's and they were all white too. What does this mean, too hot of a plug? I used a .050 gap...hmmm

 

Matt - Lean, too much timing, etc. Its exactly what you said - too hot. First, I tried bringing my gap down on the TR55s to .040". Right now I'm running the TR6s @ .040". However, I haven't dynotuned my car yet so I might be correcting changes that stem from bad tuning in the first place!

Ryan

 

Lonnie, You are the MAN! Thanks for the Detailed Response broh. I had asked a few folks about this and no one could give me a good response...Until you

Thanks,
Claude

 

Note that a colder plug will only stop detonation if the plug was actually causing it. The plug does in no way lower the combustion chamber temp...only the plug temperature.

Claude..... any time, glad I could help.

 

I thought it help reduce a bit the combustion temp since it breathed through the plug a bit...

 

The ground strap coloration will indicate whether the plug is too "cold" or too "hot". A color-break line should be right at the middle of the ground strap along with coloration along the base ring. Most normally aspirated engines will make best power like this where as others may not.

Take care

 

Ok Guys tell me.....I pulled the plug out of my car yesterday and they were white .....they are gapped at .55 what should I gap them at....Its a NA engine.....would I benefit by changing the gap???? This is kinda interesting....