It has come to my attention that I stated a 1/4" drill would leave threads......not so...at least not enough to satisfy most! Use the correct drill size for tapping.... #7 or 13/64ths.... I THINK!! ggg Matt Nall '69 stocker, '66 vert, '65 v8, '66turbo, Vairboat, Sandcar, 64 cp ALLVAIR! Timogen was a softy!