You are soo wrong!!! There are two functions of a spark plug. First is to Ignite air/fuel mixture and second to Transfer heat from the combustion chamber . The spark plug works as a heat exchanger by pulling unwanted thermal energy away from the combustion chamber.

 

how exactly does a spark plug pull unwanted thermal energy from the cc? i thought thats what the exhaust valve is for...

 

The rate of heat transfer is determined by:

1)The insulator nose length
2)Gas volume around the insulator nose
3)The materials/construction of the center electrode and porcelain insulator
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Aspark plug's heat range has no relationship to the actual voltage transferred through the spark plug. Rather, the heat range is a measure of the spark plug's ability to remove heat from the combustion chamber. The heat range measurement is determined by several factors; the length of the ceramic center insulator nose and its' ability to absorb and transfer combustion heat, the material composition of the insulator and center electrode material.
The insulator nose length is the distance from the firing tip of the insulator to the point where insulator meets the metal shell. Since the insulator tip is the hottest part of the spark plug, the tip temperature is a primary factor in pre-ignition and fouling. Whether the spark plugs are fitted in a lawnmower, boat, or a race car, the spark plug tip temperature must remain between 500C-850°C. If the tip temperature is lower than 500°C, the insulator area surrounding the center electrode will not be hot enough to burn off carbon and combustion chamber deposits. These accumulated deposits can result in spark plug fouling leading to misfire. If the tip temperature is higher than 850°C the spark plug will overheat which may cause the ceramic around the center electrode to blister and the electrodes to melt. This may lead to pre-ignition/detonation and expensive engine damage. In identical spark plug types, the difference from one heat range to the next is the ability to remove approximately 70°C to 100°C from the combustion chamber. A projected style spark plug firing tip temperature is increased by 10°C to 20°C.
Keep in mind the insulator nose length is a determining factor in the heat range of a spark plug, the longer the insulator nose, the less heat is absorbed, and the further the heat must travel into the cylinder head water jackets. This means the plug has a higher internal temperature, and is said to be a hot plug. A hot spark plug maintains a higher internal operating temperature to burn off oil and carbon deposits, and has no relationship to spark quality or intensity.
Conversely, a cold spark plug has a shorter insulator nose and absorbs more combustion chamber heat. This heat travels a shorter distance, and allows the plug to operate at a lower internal temperature. A colder heat range is necessary when the engine is modified for performance, subjected to heavy loads, or is run at a high rpm for a significant period of time. Colder spark plugs remove heat quicker, reducing the chance of pre-ignition/detonation. Failure to use a cooler heat range in a modified application can lead to spark plug failure and severe engine damage.

 

agreed... 3923's are said to be good for 5 hp as well... of course you'll never feel it but that's what I've read.

 

Thanks for the backup Steve.

Its all about the "colder spark plugs remove heat quicker, reducing the chance of pre-ignition/detonation" as is explained correctly above by the Scientist.

IndyD

 

I'm putting inthe regular Champions today I'll post back by this afternoon. I neverknew that a plugcould beso compliticated, and lead to so many problems.Thanks to All !!

I'll post back this afternoon.

 

regular autolite 3923's... no problems... tried & true on thousands of magnum motors...

 

Alright replaced with the Reg. Champions, sorry Steve I didn't read your post until now. Roughness is still there not as bad. The end off the plug was like white, all dry and no oil. The exhaust has a slightgas smell to it. any ideas. I guess my next step would be plug wires, cap and rotor? Also there is a noise coming from the back of the engine compartment. Either back by the distributor/O2 Sensor area or the place where back in the day a carburetor would be. I got my ear as close as safely possible to the valve cover as possible and all quiet. Someone told me that I needed a valve job. The noise is almost like a PCV valve when it chatters.

Any thoughts are welcome.

As much as I would love to trick this Baby out right now it is my wifes ride, so I'm not looking at performance mods. By the way Steve your Truck is awesome!!!. Indy next time i'm around Castleton I keep my eyes open for your D.

 

thanks!

get a mopar cap & rotor, MSD 8.5 superconductor plug wires & you'll be set. the white tips to me sounds like weak spark, the smell out the tail pipe also points to weak spark. I'll bet your cat is working overtime to keep up. if you done correct it soon, you'll be needing a cat not too long after.

 

why do you recommend running colder plugs rather than stock? j/w