416 rejetting issue

[xNOILABOYx]

i had a 400 w/ WB R4 slipon,which seemed to be jetted fine,after my je 416 kit and stg 2 hotcam i fould my first plug and its BLACK,did anyone else have to rejet when gettin a bigger bore or is it just because the plug was old

[duke416ex]

Yea, you need to rejet when getting a bigger bore. When I went to a 416 I went from a 154 jet to a 165 jet, but I had a full port and polish.

[cals400ex]

was it black after checking the plug at idle, mid throttle, or full throttle?