Spark plug heat range
03-14-2016, 09:45 AM
#2
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I have NGK FR5 but my engine is not stock. I also have AFR 195 heads. Be aware that heat range numbers can go either up or down depending on manufacture. Eg. AC Delco plugs get colder as the number goes down - R43 is colder than R45. NGK is the opposite.
03-14-2016, 09:45 AM
#3
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-8 is the "base" race plug for most folks. They number things "backwards"...so on the street a -7 or -6 or so works well. I like hot plugs for street stuff...in fact my 555"/871HP ran extended tip hot plugs even when racing usually.
JIM
JIM
03-14-2016, 09:56 AM
#4
Le Mans Master
I run 5 heat range most of the time in NGK. Aluminum heads 9.9 CR at 4000 feet.
Street driving not racing.
Street driving not racing.
Last edited by REELAV8R; 03-14-2016 at 09:58 AM.
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03-15-2016, 01:58 PM
#5
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03-15-2016, 02:24 PM
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What compression are you running? Aluminum or iron heads? There are several things to consider when picking a heat range. Too cold and they foul. Too hot and you might get pre-ignition.
03-15-2016, 05:53 PM
#7
aluminum heads
the 7's were fouling, gonna try 5's
how will i know if pre-ignition happens
03-15-2016, 09:31 PM
#8
Le Mans Master
Detonation is usually first.
You can hear detonation as a distinct rattle or metal on metal type sound, or sometimes marbles in a tin can sound, usually under load. If allowed to continue it can lead to pre-ignition.
By looking at the plugs you can see little black specs or little shiny specs on a very white porcelain of spark plug. You may also see some of the ground strap melted away or a portion of the porcelain broken and missing.
Last edited by REELAV8R; 03-15-2016 at 09:32 PM.