I was talking to a machine shop owner today and he brought up that he had used a product called full torque thread inserts for repairing main bearing bolt holes.  I checked out their website  http://fulltorque.com/  and they show inserts specifically for this repair.  Has anyone heard of or used this product?  Could it be a way to save some of the 312 blocks that are cracked at the bolt holes?   Randy

I have used these in some applications, but not in main bolt holes. But I think you could try atleast?

http://www.emhart.com/brands/heli-coil

 Seppo from Järvenpää, Finland
www.hollowheads.net (just click the hole in the head to proceed)

I dont believe you could use these thread inserts with any kind of confidence in the 312 main web bolt holes, if the web is allready cracked, and usually is because of less material around thread area, then tapping old thread bigger to accept coil insert would remove more material and weaken it more? maybe have another look at situation. These are only my thoughts based on fitting many inserts, heli coils, etc. merry Xmas everyone.

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

On their website they specifically show these used for main bearing bolts, they state that they work different then standard helicoils due to thread profile on the outside.   I may try an experiment though on one of the bad blocks I have.  Randy

Randy: It may depend on how deep the crack is, which may be hard to ascertain. If I recall there was an article on the problem in YBM, & in some cases the crack could intersect an oil gallery or coolent area. Maybe someone who has dealt with these problems (I have not) can comment for sure. Also, apparently it's possible to in some cases drill main bolt holes a bit deeper & thread them further. Again I have not any experiance with it..

Paul