I ran into the Ford F series truck water pump problem. I have a 1994 F150 with a 351W engine. One of the water pump/timing cover studs was so seized up that it broke before I could get it out. I tried an Easy-out, almost broke that. Probably because I drilled the pilot hole slightly off center. So I tried to enlarge the hole and get the bolt to collapse. No luck. During that process I caused the hole to be not only off center but off axis too (no longer perpendicular to engine block). Helicoil didn't look like much of a solution (because of that hole), but I tried it anyway. No luck. JB weld time. I filled the hole and covered the end of allthread (same size of original bolt) and stuck the allthread into the hole. The allthread is being held in place by the power steering/ac condenser bracket (through which stud portion of the original bolt went). The original bolt is 5/16"-18TPI. The hole I drilled and tapped is 21/64". New allthread is same size as orginal bolt, I'm just planning on using a nut to secure the water pump and timing chain cover. Every thing in contact with the JB Weld was religiously cleaned with acetone.
Do you know if this is going to hold, or should I just call the welder to weld up the hole and give me another chance at drilling straight. Can that even be done? The engine block is thinwalled cast iron.
Thanks for reading!