Hey Simon, that is a real concern for us. When you fill the block with "grout" it only comes to half way up the water pump holes in the front. When filling, you have to do one side at a time with the block leveled, using an air rattle gun, or just a small hammer, must keep the grout settled in the block. Bolt on a head to keep things square, the after it is dry in a day or two, do the other side. When running the water still goes in the heads and intake and partial cooling of the cylinders that are exposed above the grout. Most race car engines only run for about two or three minutes max and do not get in the danger zone, especially if they run methanol. Why do it, some other brand engines have real thin wall's and are bored as much as .150 oversize. The grout keeps harmonic's and cylinder distortion to a minimum. Some of the older funny cars and dragsters, did not run any coolant at all, or sealed it in with no radiator etc. Street applications are out for the above methods.
