Hey guys I have a 505" six pack motor... took it on a long run today... 120 miles, and now cyl's 1 & 4 have rich fouled plugs(black soot). All the other cyl's plugs are tannish brown color... What gives??? How can just those two plugs foul like that?

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1971 Roadrunner FJ6 Sassy Grass 505"RB, 18 spline 4 speed, and Dana 60 with 3.54
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