Hello All, I have a 1968 340 in my Valiant and just installed a paxton supercharger

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disco

disco

Daddy Dave
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St Thomas Ontario
It has eddie rpm performer alum heads and they recommend that I run 1 to 2 degrees cooler sparkplugs, any help as far as brand or number would be helpfull.
Thank you
 
disco said:
Sorry I dont have pics but There NGK BKR5E
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Many FABO members can ""read" the plugs to see how they are burning. This is how many people determine if you need hotter of cooler plugs. See example below:

spark-plug-lean-rich-optimal-640x360.jpg
 
Edelbrock is suggesting Champion RC12YC for a plug in those heads. What you have is the NGK equivelant of the Champion plug.

Below is a chart of NGK heat ranges. The larger the number (i.e. 6 is colder than 5 etc). I believe Champion is opposite of that, smaller number is colder.

If it were me, I'll take a NGK copper core over a Champion and try a heat range of 6. My 360 magnum calls for the same plug as yours and I had pinging issues with it. I changed to a colder NGK plug (6) and solved the problem. Every application is different, you're going to have to learn how to read the plugs to know if you have the correct heat range if you don't already know how. Hope this helps.

ngk spark plugs heat range - Bing images
 
You'll have to play with it. Having boost changes things some. You'll need a tighter gap. My turbo'd cars use iridium plugs.
 
Treblig said:
Many FABO members can ""read" the plugs to see how they are burning. This is how many people determine if you need hotter of cooler plugs. See example below:

View attachment 1715440733
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This is why reading plugs can be a bit tricky. The plug on the left doesn't look lean to me. That plug is way too hot and you can see the fuel on the plug that is being thrown in there to cool that plug.

This is also why an O2 sensor can trick you. I'd bet a everything I have that the A/R with that plug and tune up is what most would consider "normal" or correctly tuned, when in reality it is dead rich with a hot plug and the O2 sensor doesn't know the difference.
 
I’m pretty sure the RC12yc cross’s over to ngk 5 series. My BB Eddie heads recommended the 12yc plugs too, I am also running one cooler ngk 6 series. I’d have to go look but I think they are ngk-br6e? Or 6es?
Let me know if you want me to go to the shop to get the part number.
 
yellow rose said:
This is why reading plugs can be a bit tricky. The plug on the left doesn't look lean to me. That plug is way too hot and you can see the fuel on the plug that is being thrown in there to cool that plug.

This is also why an O2 sensor can trick you. I'd bet a everything I have that the A/R with that plug and tune up is what most would consider "normal" or correctly tuned, when in reality it is dead rich with a hot plug and the O2 sensor doesn't know the difference.
Click to expand...

Same here !!
 
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