I would like to switch over from my AC Delco Spark plug R45S to a NGK Plug. My car is an all stock 1969 Cutlass with a 350 Cubic Inch, 4 barrel V8 with 10.25:1 compression. Both Advance and Autozone say to use the NGK XR4 #5858 spark plug. Bill Trovato's book recommends the NGK XR45 spark plugs. What plug does every one recommend?

Thanks,
Noel

 

I use XR5’s in just about every iron headed build I do.

 

That would be the correct NGK Spark Plug. https://ngksparkplugs.com/wp-content...rence_2019.pdf