When you say race block, how much HP is the goal? Myself personally have seen too many bad outcomes from pushing a substandard engine block. Any engine I build over 600HP preferably gets an after market block. Or an OEM block with filler and good maincaps and girdle. If I was going to use it, I would do a block fill with moroso block filler or similar product. The next question is how and why did it crack? Was it from freezing? or did it do this in a race car? I had a 440 block crack like this, with filler in it already, and the cylinder wall were barrel shaped when I took it apart, so in other words the cylinders swelled and pushed out the side of the block. If from freezing, how round are the cylinder bores?
It was in a low HP street car a guy had bought, I'm sure it froze at some point before he got it. I would use it for an NHRA Stock 383 so the HP would be in the 475-500 range, the cylinders are .300" + thick which makes it a better block than the standard block I have filled now that I'm getting ready to machine over the winter. I have been using Halco machine grout for about 30 years now, it does not expand, I have taken many samples when filling a block and put them in everything from a plastic cup to a spay can top. The cylinder condition is unimportant as I'll be boring it at least .125" over.
