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What would cause this??
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[QUOTE="JGrossijr, post: 1152417, member: 57946"] Most common causes of a melted plug. 1. Jetting too lean 2. Wrong heat range plug (too hot) 3. Spark timing too far advanced I would A)make sure that the jetting was close to stock if the motor has not been modified, and read the plug porcelin at its base for a jet reading, B) Get a stock heat range plug in it if the compression has not been raised (colder if it has been raised), C) Make sure that the spark timing is at the factory setting. D) Pull the head off and make sure that the piston has not been melted. Spark plugs either fire, or they don't. If they foul they will not fire every time, and if they melt they won't fire every time. There is an ideal temperature range for a spark plug to operate within. If the tip does not get hot enough to burn the carbon off the plug will foul, and if it gets to hot it will melt. To regulate the tip temperature plugs bleed heat off through the threads to the cylinder head. A slow bleed off (hot) is necessary to get the plug temperature up in a lower compression or lower output application. Conversely, A spark plug in a cylinder that has more compression, or builds more heat due to a higher output, will need to bleed the heat off faster (colder) to keep the plug from melting. In the case that a plug gets over temperature it will become glowing red hot before it melts. At this point it is hot enough to ignite the mixture in the combustion chamber prior to the plug actually firing. This pre ignition in turn sends combustion chamber temperatures soaring. From there chances get pretty good of melting and/or siezing pistons. This can also cause detonation to the point of breaking pistons, rods, cranks, etc. The Moral of the story is this. Do not use spark plug heat range as a tuning aid. Use the appropriate heat range for your application. This is generally dictated by compression ratio, and can be verified by reading the plugs. On that note, use the color at the base of the porcelin where it meets the steel shell of the spark plug for jetting determinations. Use the ground strap of the plug for heat range determinations. You should see a heat line on the ground strap at the midway point in the bend. If the heat mark is at the tip then the plug is too cold. If the heat mark is at the end near the threads it's too hot [/QUOTE]
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What would cause this??
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