On Tue, 27 Jan 2015 11:17:59 -0500, Stormin Mormon
burns off and the insulator is white. With leaded gas sometimes the
tip would go yellow/green if there was too much sulphur in the gas.
Semi-conductor (Lead sulfide?) plugs don't fire too well. (ever heard
of Galena? it was used as the detector in a lot of old "cat's
whisker" crystal radios of yesteryear.)
It appears neither of you knows much about IC engines . I stand by my
statement , it is a possibility . Might not be likely , but possible . "Hey
Bubba , these here plugs iz only a little shorter than the plugs we took
outta your Triton motor , less use 'em !"
Most small engine plugs are similar. Especially if they are either 2 or 4
cycle types. If the heat range is not hot enough they may foul out after a
while and need cleaning. If too hot they may burn the piston. Not sure how
much hotter or colder they need to be and how long the engine would need to
be ran to do either. If much shorter the spark may not be in the right
place for the engine to run or run very well. If it were mine, I would
check to see if the part in the cylinder was longer. If not, I would try it
and change it out at the first time I could.
The gap will not effect the heat range. It mainly determins if the engine
will run or not run. Too far open and there will not be enough voltage to
jump the gap and you mght as well not have the wire connected to the plug.
Too close and there may not be enough spark to ignite the fuel.
If you look at most plugs of the same general type, the heat range is sort
of determined as to how long the part that is outside the cylinder is.
That is the usually white material between where the wire is and the top of
On Tue, 27 Jan 2015 18:08:04 -0500, "Ralph Mowery"
One thing I never understood about spark plugs, is WHAT DETERMINES THE
HEAT RANGE? Is it the length of the spark, (but that would be the gap),
or a built in resistor to cut down on the spark voltage, or what?
My understanding is how much plug body retains heat. Nowadays we have
Platinum or Iridium plugs which lasts LONG time. I usually roast old
plug laying on the rnage heating element. The when it is still pretty
hot install it ahs try to start the engine.
On 1/27/2015 7:27 PM, email@example.com wrote:
Been a LOT of years, but IIRC it's the length of the
ceramic insulator in the center. Of course, tomorrow
I'll try and remember to web search the question.
Longer insulator is hotter plug.
Christopher A. Young
learn more about Jesus
You can say it until you're blue , some just can't grasp the concept of
heat transfer path . Shorter path equals colder plug , longer is hotter .
Ever seen the top of a piston subjected to extreme pre-ignition ? I've seen
I have too, What you are possibly not catching is HE is saying it is
the length of the insulator OUTSIDE the engine - from the shell to the
terminal. He is WRONG - I'm sure you will also agree. It is the
insulator INSIDE the cyl.
Remember - I've been a mechanic for decades and taught motor vehicle
technology at the post secondary and secondary level.
I admitt I was wrong in my statement about the outside of the plug. The
outside of the cylinder part of the plug does get rid of some of the
heat,but it is mainly the part that is inside the cylinder of the plug that
determins the heat range.
I mainly had it backwards to start with.
The heat range is how hot in temperature the plug gets. Mainly the length
of the length of the plug sticking out of the engine to the plug wire. Too
cold and carbon or other junk builds on the plug usually shorting out the
spark. Too hot and the engine will not shut off when you cut the power to
the plug off. Makes it a diesel type engine.
The resistor part is to help supress electrical noise that you may hear on a
radio. Same as resistor wiring in a car that goes to the plugs.
Not quite. A ptojected nose plug sticks the tip of the electrode out
into the cyl where the air/fuel charge helps cool it, giving a wider
heat range. The thermal path between the tip and the shell still
determines the heat range. - but Ralpf has his plug science Bass
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