anyone on here running 12.5~13.0:1 compression ratio on a ls/vtec?? if so what spark plugs did you run on that motor?? i am building my ls/vtec and its a 13.0:1 compression ratio. i put ngk-r spark plugs there 11s. so my motor would die on me when i started it. it would run for like 5 minutes and then die on its own. i took out my spark plugs and its like the piston hit the gap on the spark plug and bent it to where it was touching the electrode so now im wondering what spark plugs to run? anyone got any ideas?? i want to run the hottess spark plug i can thanks!

 

Try an NGK r5671a-8 or a Champion C61cx (cut back ground, better plug IMO). If you want a colder plug try the r5671a-9 or c59cx--hotter try r5671a-7 or c63cx. I would start with the NGK 8 heat range or the Champion 61 heat range--if going with 13:1 compression.

 

im running 12:5 CR and im using the NGK r5671a-8 plug as we speak. The 7's were a little too hot so i went teh next stage higher and havent had a problem since!

 

im running ngk 7 in mine ctr piston gsr block and its finnd for three months going

 

Yeah alot of people seem fine with 12.0-12.5:1 with an NGK 7 heat range plug. I have always used an 8 range NGK or 61 range Champion at 12:1 --seems to work well.

 

cool thanks you guys i juss put in the ngk-7s and they are working pretty good i think ima try the ngk-8s next and see how they work

 

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If the 7's are in and working well and when you "read the plugs" and look at the color mark on the ground strap, if it's at the mid point, changing them to 8's will have no advantage. You change plugs based on how they read, not what people say.