I wonder if the head bolts are bottoming out? The block looks to have been milled. The head bolts bottoming out could certainly cause that. Also, trash or even a small bit of water or other liquid in the bottom of the bolt hole could even cause it when the bolts are torqued down. I've actually not seen that before. I agree after seeing the picture. I wouldn't use it, unless I had no other alternative.
easy to sort if they are, just add a hardened washer to each bolt.
I've seen both blind holes and open holes in small blocks....and had people argue with me. But I've seen it. I've also torn down more engines than a lot of people have ever even seen. I was the tear down rat for a mom and pop machine shop when I was a junior in high school through my early 20s. I tore down a BOATLOAD of engines. It was a LOT of fun though.
Boy that's a lot of work drillin and tappin all those head bolt holes for inserts in a cracked block. I'd add flat washers and put sealant on the bolts and run it as it before I did "ALL THAT".
i thought there were only a couple like it so the inserts would be more of a permanent repair, if there's lots and another block's not an option then yes i'd go with washers and sealer too. you've got probably better than a 50/50 chance it'll be fine which i'd take.
