spark plug heat range questions.

[slantsixdan]

the tips of my ngk v-power zfr5f11's had white on the very tips of them when i pulled them out, wich i thought was a little strange. So that means my engine was pingin if there was white on the tips of the insulators?

No. An off-white deposit on the electrodes themselves is a result of the particular chemistry and additives in the gasoline you burn. What you're looking for is bright white spark plug insulators (the porcelain part inside the threaded shank) and tiny globs of metal. If you don't see that, it means the spark plugs are not running too hot.

The one and only purpose of octane is to prevent ping. There is zero benefit to running fuel of octane rating higher than required to prevent ping in your particular engine, in your particular car, at your particular altitude.

 

[pjc360]

so are you saing my 360 magnum with 14 degrees of initial timing and 9:0.1 compression ratio could run on 85 octane fuel and be completley fine?
Because where i live regular gas octane is 85, plus is 87 and premium is 91 octane.
I have read and heard of alot of the 1994 to 2002 dodge trucks with 318 and 360 magnums pinging on 87 octane fuel and they are fuel injected and have computer controlled timing. My engine is carbureted with fairly high initial timing setting. I have always been to afraid to rn 85 or 87 octane fuel in this magnum. Mainly because it has had 91 run thru it all its life. I guess i could try the 85 octane, but my girl friends 2009 chevy cobalt with a 4 banger rattles on the 85 octane fuel. Her cobalt runs better on 87 octane fuel vs the 85 octane fuel. When it has 85 octne fuel in it and you start it up cold it rattles and knocks untill it warms up, but if it has 87 octane fuel in it and you start it up while its cold it doesnt rattle or knock.
so i figured since a 4 banger couldnt handle the 85 octane fuel that my 360 most likely wouldnt like it ether.

 

[slantsixdan]

so are you saing my 360 magnum with 14 degrees of initial timing and 9:0.1 compression ratio could run on 85 octane fuel and be completley fine?

Maybe! Try it and see. If it pings, go to mid-test (87). If it doesn't, keep running 85 and pocket the $$ difference.

Because where i live regular gas octane is 85, plus is 87 and premium is 91 octane.

Right. That was how it was up at 5500 feet in the Denver area where I lived for 20+ years, too. Increased elevation --> reduced air density --> reduced combustion chamber peak temperature --> reduced need for octane. The 85-87-91 fuels available at high altitude are functionally equivalent to the 87-89-93 fuels available at sea level.

I have always been to afraid to rn 85 or 87 octane fuel in this magnum.

No reason to be afraid. Drive the tank almost dry, put in a few gallons of regular, and keep your ears open. If it pings, go fill it up with high-test. If not, keep buying regular. Drive it til the tank's almost dry, then put in a few gallons of mid-test, and keep your ears open. If it pings, go fill it up with high-test. If not, keep buying mid-test.

my girl friends 2009 chevy cobalt with a 4 banger rattles on the 85 octane

...which has nothing to do with your car.

so i figured since a 4 banger couldnt handle the 85 octane fuel that my 360 most likely wouldnt like it ether.

That is not how the world works.