Cleaning out one of my storage areas and have a standard bore '57 312 block that I managed to strip out the last 1/2 inch of threads for one of the main bearings. Did this many years ago in my mispent youth. Used a longer bolt and some washers and put it back togeather. Ran it till the rings went south. Question is can it be repaired properly with a heilicoil and hold up? Hate to scrap it if it could be repaired. It would also need a rebore if I ever had to use it. I have a couple of 292 blocks I could use if I ever need on. Should I save it or scrap it?

Repair with a Tyme Sert, easy job

I used an insert to repair a block to attach a head. An end one and could not fit a 1/2” in the spot so I used a 7/16” and a stud. I run 14-1 on that in-line engine and it’s been fine. As long as you have the meat on the main web for the threads of the insert you should be fine. I like them because you are now bolting into the steel of the insert.
I actually did it in the car by renting a large mag base drill and buying the one correct bit and borrowed the correct starter and bottoming taps.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Time Serts have a thinner wall and would be the ideal fix for a stripped 312 main bolt hole.  A helicoil is a potential fix assuming that the new threads for the helicoil do not break into the bearing journal surface.  Helicoils are made in different lengths so if going this route, use a longer than standard length helicoil.  Stacking two shorter helicoils together in the hole is also another option to get more thread area if there is difficulty in obtaining the longer helicoils.

Lorena, Texas (South of Waco)