I do not know the history of the block,  I bought it to rebuild.  The person that I bought it from had it magnafluxed at a shop but I don't know what process they used, apparently they did not know where to look on these blocks. The cracks intersect both the cam journals and oil galleries to the cam bearings.  I don't believe there is any way to repair it.

Questions that occur to me;  Was the engine likely in service a long time with those cracks? Are they likely to get worse ?  And do they intersect an oil gallery? Sometimes small cracks can be stopped from migrating by drilling a small hole intersecting the end of the crack. Just random thoughts..


Paul

those type of crackes can be repaired if you use the harmend chain lock system. findeing some 1 that still does the prosedure will be a isue.years ago several shope  in vancouver wher repairing diesel heads,as well as d8 cat trans housinds,this proses is stronger than original aria. 
if you ar near western canada i could look see is any 1 hear still does it.the chain locks go acros the crack,so it is far better than the taperd plugs,that just work in small cracks in non stresed aria.

Man o man, another thing to check for before assembly.....

Lets see now..... Ah yes, #26 on the list. One of these days that list has GOT to be complete.....?!?
Rowen

Rowen
55CV
Woodland, Ca

UGH!  I'm shaking my head.  What I haven't even been looking for!  DUH!    

THANKS for sharing the information and pictures.  Much appreciated!


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Well I guess another '57 312 block bites the dust, did a dye penetrant test all three webs are cracked. You can see two in this picture.

Would getting in with a die grinder and sanding help to clarify things?

Ted, Thanks, I think it would be very unusual also.  There aren't any visible cracks on the webs.  I am going to perform a dye penetrant test on it just to be sure, if it passes I am going to call it good. 

While cracks are known to occur in the cam to main webbing areas, having all three cracked at one time is unusual.  If you don’t see the cracks in the main or cam bearing bores themselves, then the marked areas being cracks is in doubt.  Casting seams can be mistaken for cracks when doing magnafluxing so you have to be careful in interpreting the magaflux results. 
 
Here’s the picture of a crack that starts at the cam journal hole but has not migrated all the way to the main journal.  This is the #4 main webbing and the other webs were crack free.
 

Lorena, Texas (South of Waco)

Had a '57 312 block magnafluxed, the shop uses wet fluorescent process. Shop told me that it was cracked at the three center main webs in the area of cam bearing feed, a picture of the locations that shop marked is attached.  Shop did say that they did not see anything on either cam or main bearing bores. I have not seen a Y-block show cracking at this location before, but have had many cracked at the main bearing bolt holes. Is this a this a problem area or is there something in the casting that may be causing these indications?  I also find it hard to believe that all three inner webs are cracked.  Does anyone have in-sight on what may be going on?