Was talking to a guy the other day about spark plugs for my cars. Both have 440 Source Stealth heads with 10:1 compression pistons. He recommended NGK6. I checked my rides to see what the engine builder had put in. My 440 has NGK7, and the 451 has BKR5. Seems to me I should have the same heat range in both cars because they are similar builds. Also wondering if this would help so they aren't so fussy about gas and pinging.
