I was never a fan of tapping a 1/2″ hole for a 1/2″ pipe plug which measures about .530 diameter. I’ve been using 9/16-18 set screws for the SB Chevy street and race builds for years. A 9/16” starting tap will work without drilling, and I finish up with a bottom tap. The taper on the set screw bottoms nicely on the smaller galley diameter just behind the 1/2″ hole in the block. A better seal and fit.
Randy Torvinen
Torvinen’s Machine Shop
Menahga, MN
