Is this block junk with these cracks?
 

My Pontiac engine block got magnaflux'ed at the machine shop and they found these cracks between coolant holes. The yellow lines are powder. It's a small local shop so weld repairing isn't something they offer. I'd have to find somewhere else to send it to, or learn how to drill and stitch myself(not impossible, I've used power tools for years). It's just a basic 350 so I'm not trying to save a 455SD or anything.

The thin yellow lines between the yellow paint pen marks are powder, I mean. The shop left it on the cracks to show me them.

Probably get better replies not in the body shop section... try street or race.

The cracks in that location will prevent the head bolt from maintaining its torque setting over time. There are plenty of 350 blocks available. I wouldn't mess with welding it up.

Out of curiosity, is that a common place for a block to crack and what would cause a crack like that?

It would cost more to have welded than a different block would cost you. My2¢

Curious what was the machine shop's opinion was (on being junk or not)?

I would scrap it and buy a 400+ CI block. I realize things have dried up quite a bit but if you're patient and resourceful you can still find them. NFW would I dump $ into a 326/350, especially one with a crack in it.

Not worth repairing, find a 400 or 455 block if you are rebuilding.

350 block with a 4.25" crank gets you 400 cubic inches too :) And in my case, 453HP.

I had my 389 block that was cracked in 3 places repaired by "stitching" it. I did not however have cracks at a head bolt hole. I think I would pass on that block.

Absolutely repairable but idk why I have an extra 350 block . I've hit a nice 455 w aftermarket caps , a 428 and a 400 . If it's not numbers matching to your car I'd just get something else . Plenty of stuff out there