I while ago I got three out of my battery box bolts out with those craftsman easyout tools. For a while now I gave up on the fourth one which was still holding the rotted bottom of the old battery box. I took a grinder and ground down what little was left of the last bolt head flush with floorpan, center punched it and center drilled it, and then step drilled up to two sizes smaller than 3/8 16 tap size drill which I think is 5/16. I think you should use K1 when tapping cast iron, but had none, so I used some marvel mystery oil. I was so happy it all worked out great. Kept backing the tap off, blowing out hole and plenty of oil. I was surprise how deep the holes go, I checked one of the front ones before I started drilling and it seems to go all the way into the casting, like two inchs.
THANKS GUYS Paul K. in N.H.
