spark plug recommendation

[Brads70]

Found this useful ....   https://www.ngksparkplugs.ca/tech-info-spark-plugs.cfm

JonH  to answer your question about how I ended up with that plug. I'm pretty sure it was from other members on Moparts that run that same head and suggested that plug? I'll try the Champion RC12YC plugs next as they seem to be 2 heat ranges hotter if I understand it correctly?  That and I always have them in stock with my business.

https://www.ngk.com/learning-center/article/200/how-do-i-find-a-colder-or-hotter-plug

[Chryco Psycho]

so you are using the NGK R5671A-7
so is the heat range 5 or 7 ?
5 looks to be the same as the RC12YC

[Strawdawg]

If I read it correctly, R designates a racing plug so the heat range is 7 in this case.  Somewhat colder than the Champion?

[Brads70]

so you are using the NGK R5671A-7
so is the heat range 5 or 7 ?
5 looks to be the same as the RC12YC

If I read it correctly, R designates a racing plug so the heat range is 7 in this case.  Somewhat colder than the Champion?

Yes it's 7