interesting, thanks for the info. I wasn't sure what the differences were between the r7420's and th r6725's. Looks like the best plug for the rotary is the r7420 then which must be a newer plug than the r6725.

 

right on! rhdjapan.com has 7420s for 49 a plug!!

 

That's where I got mine. They gave me some sort of discount that made it cheaper but it was still expensive.

 

Dont get the ngk 7420's get the greddy's, they are the same exact plug just recased in greddy boxes. They can be found for $29-35 a plug. Mine were $29 ea with free shipping. They are not a copy of the 7420's, they ARE the 7420's.

 

I also run the R7420 (9 leading, 10 trailing) and they last a damn long time. Over 25,000 km with MANY track days at 16 PSi and recently 20 PSi with water injection. After cleaning the plugs by glass blasting them, I realized I could have reused them even longer. The only sign of wear on them was the rear leading plug had a small 1mm wear point at the end of the top metal piece (not sure the name). I believe that is because of my 1850*F rear EGT's. All other plugs looked almost perfect.

The Greddy one's are easier to find and generally cheaper. They are indeed the same plug, they even have R7420 written on them lol

thewird

 

sweet im sold, and i found a site with a pretty good price although ive have never heard of them before anyone know of them? http://thmotorsports.com/greddy/gred.../i-177763.aspx

 

http://www.gtoctane.com/product_info...ducts_id=75982

heres a little better price, be sure to compare shipping rates also. I think this one is free shipping.