nope not milled to hell only .015 shaved from stock only reserfaced but im just lil on the safe side im not useing homedepot im going to slide spaces off other spark plugs i would not use a washer it will not seal i just would like at least 2more threads up for safty my valves are perfectly free of harm from claying it but i just want the plug lil higher and was thinking maybe a d15 iss a bit shorter or even typeR or something i just thru this up to see if someone hard some sohc and dohc and could hold them 2gether at let me no you can kinda see from the picture the head i not shaved but i have flat Ss valves