I know that no web cracks is whats preferred. I just pulled apart my 87 block and all 3 center webs have cracks about 1/2 an inch long. I pulled apart a 1984 block I have that dropped a rod, and it has cracks on the 2nd and 3rd main only on one side. About 1/2 inch again. The others look ok. I have a line on a 1984 doner truck, but am probably gonna go through a lot of work to find more cracks.
I was planning on installing a main stud girdle on rebuild before I found the cracks.
Since probably most every block I find will have cracks, how much is too much? and has anyone found a way to stop them from spreading that actually works.
The 87 block is in great shape and I was hoping to rebuild it, the 84 was for spare parts and will need some bore work, like maybe a sleeve from dropping a rod.

I did build one, with the owner's full knowledge and permission, that had 1/2" cracks on two main saddles. I used the DSG girdle, had the mains line honed with it torqued in place. So far, so good! It's been two years, don't know how many miles but quite a few.

This build care about after tearing down several cores, looking for a block without cracks. The one I built had the least wear and cleaned up good.

thanks for the info.
has anyone tried to tig the cracks?
I have an arc, mig and tig. I suck at arc, but could see tig doing it the coolest and least grinding.
I've searched welding cast and there seems to be a different opinion on how to do it from almost everyone

When I was going through automotive school, we were taught about welding cracks- mostly on cylinder heads, but also on some cast iron blocks.

You'll want to use a center punch, and put a good dent at the end of the crack; this is supposed to help stop the crack from spreading. Then use a pencil grinder to open up the crack some; about an 1/8 of an inch on either side of the crack. Fill the gap with your bead, then grind it down flat. (grinding it flat keeps it from being a focal point for heat, which would probably cause the same area to crack again)
I don't know how important keeping the temps down will be- I've only done this a handful of times, and never on a head that would get used afterward. It was purely for educational purposes. FWIW, all we had was an old Lincoln arc welder, and it worked great.

thanks for the info.
called some welding shops that specialize in exotic welding, they think its possible, and a supplier of specialty rod for cool welding where the block doesn't need to be oven heated etc. the rods are about $125 a box. it sounds like it can be done with the proper prep work. if this were steel, there wouldn't be any concern about welding up cracks.
called a few rebuild shops and they never fixed, just tossed em, but don't even know where to get a good block anymore.
it would be informative to hear if anyone tried to repair the cracks and if it held up in use.

I know that no web cracks is whats preferred. I just pulled apart my 87 block and all 3 center webs have cracks about 1/2 an inch long. I pulled apart a 1984 block I have that dropped a rod, and it has cracks on the 2nd and 3rd main only on one side. About 1/2 inch again. The others look ok. I have a line on a 1984 doner truck, but am probably gonna go through a lot of work to find more cracks.
I was planning on installing a main stud girdle on rebuild before I found the cracks.
Since probably most every block I find will have cracks, how much is too much? and has anyone found a way to stop them from spreading that actually works.
The 87 block is in great shape and I was hoping to rebuild it, the 84 was for spare parts and will need some bore work, like maybe a sleeve from dropping a rod.
do the cracks go deep into the webing? if not you may be able to save the block buy installing splayed caps.

the AM General blocks are good if you can find them