DPR 8Z or 9Z ?

[promisc]

My dealer give me a DPR8Z when i ask them for a 400ex sparkplug. Is the DPR9Z better than 8Z? Also, how to correctly gap the plug?

[Silverfox@C&DRacing]

We just talked to JE Pistons about this. They said for the big bore kits you need to run a cooler plug. I am going to try the DPR9Z. if you still have stock compression I would run the 8 plug.

[YLW400]

I agree with Dusty, I tried running a 9Z for a while, and I kept fouling them. I went back to 8Z, and haven't had a problem. By the way, I have stock bore..

[YZROOSTINYA]

I run a 9 in the summer and 8 in the winter

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