I can’t seem to find information online regarding the relative performance difference between the R7437-9 (4654) and R7438-9 (4656).
There isn't... NGK basically has zero marketing info for their racing plugs. They don't even try to convince you how their racing plugs are worth $35 lol.
the 7s are a traditional projected tip vs 8s which are recessed / non projected. You see the non projected style used for true race plugs or high heat applications like big nitrous shots etc. They are great to reduce the chance of pre ignition and overheating, but like everything in life there are tradeoffs..... they will probably foul up faster, not as efficient combustion in normal driving/cold starts etc. So in my mind, I went with the 7s for a daily driver/stock block setup. Once you start to push it so far you have to accept more and more tradeoffs, but I think for typical 400-500 hp build, no reason the 7s won't be just fine. Lots of guys in the 500-600 range running them too. If I was going to track the car regularly I would probably get the 8s... my 2 cents.
I think you may be confused on which 7s he’s speaking about, Jim.
These are both the NGK Racing plugs priced ~$35-40/plug. R7437-9 & R7438-9
Plus Rock Auto charges for shipping. Napa usually has them in stock for the same price. FCP least expensive in the long run. Still don't get how FCP can afford that.
Same heat range. Read Aaron’s post againYou are correct. I was thinking of the stock plugs. So the two racing plugs mentioned are just different heat range?
There isn't... NGK basically has zero marketing info for their racing plugs. They don't even try to convince you how their racing plugs are worth $35 lol.
the 7s are a traditional projected tip vs 8s which are recessed / non projected. You see the non projected style used for true race plugs or high heat applications like big nitrous shots etc. They are great to reduce the chance of pre ignition and overheating, but like everything in life there are tradeoffs..... they will probably foul up faster, not as efficient combustion in normal driving/cold starts etc. So in my mind, I went with the 7s for a daily driver/stock block setup. Once you start to push it so far you have to accept more and more tradeoffs, but I think for typical 400-500 hp build, no reason the 7s won't be just fine. Lots of guys in the 500-600 range running them too. If I was going to track the car regularly I would probably get the 8s... my 2 cents.
So the R7438-9’s? These or the equivalent Denso IKH-0127 are what EQT advised I run. For reference, this is my daily that I drive about 10k miles/yr.I've had the new non projected tip NGK iridium plugs for a few thousand miles now and they are working great so far