plug heat range
#5
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Location: Little River SC
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For a gasket style plug,forced or natural induction. I always try to use a NGK R5672A-8 this is either for alum. or cast iron heads. To use a non projected plug is going to shroud the spark in the combustion chamber. I believe; you need enough heat range on the ceramic to control plug fowling at idle, but not at off idle or higher rpms. A/F ratio needs to be correct in order to prevent fowling, detonation and pre ignition. This also pertains to compression ratio, timing, fuel octane # and what is the water temp when idling. If a piston dome interferes with the plug electrode you would either index it or use a non projected plug. I know in the past Merc used like a MR 43, I believe this was maybe due to fuel back then and now we are needing the engines to burn cleaner. Maybe a little to much info. Hope this helps.
#6
Charter Member #1171
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Ngk br8
a/c 41t
But those were no where near the HP motors that I know your asking about !!!!!
a/c 41t
But those were no where near the HP motors that I know your asking about !!!!!
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