Spark Plugs

I cannot understand why the newer books list RN12YC plugs for a 340, an engine with that much compression should use a cooler plug RN9YC.

RN12YC's are for an engine with lower compression 9:1 like a 318/2bbl.

I had the same issue with Champion Platnium Plus plugs I bought for my engine, the ones listed for car are the hotter plugs.

I have used the champion RN9YC, but actually prefer the Accel 114 u-groove plugs I used last season.

bob