A crack in that position is not uncommon on a 250, and sometimes the same thing will be found on 230 engines. The block is a bit weak there, and even normal head bolt torque will sometimes result in a crack. Most experienced engine builders reduce the torque on that bolt by about 10%. It's way out on the corner, where a little less torque won't cause head warp or head gasket sealing problems. It almost always migrates into the head bolt thread. Since that one doesn't seem to have made its way to the water pump opening, it's probably fixable. Find the end of the crack, and stop-drill it to keep it from spreading further. Tap the hole for a machine screw- - - -8-32 or something similar. Then install a Heli-Coil thread insert into the head bolt hole. V-groove the crack and fill it with brass to prevent a coolant leak. Unfortunately, the above fix will require a teardown to the bare block, and a full rebuild.
Jerry
