I won't use block filler again under any conditions, never again, not good I redid and them made another complete motor for a NHRA stocker racer, the original block was filled to about 1/2 way up the cylinder walls by the formwer engine shop. We, me and the dyno operator, where dyno testing the first motor when the dyno owner came out with a infra red temp gun and read the side of the block, he ask us why we where running the motor so hot We had set the water temps running between 110 and 120 F set off of the dyno cooling tower. He had read the side of the block and below the cement was 180 F and above the cement fill line was 110 to 120F I didn't fill the new motor and it made the exact same HP and torque with the same heads, intake, carb and camshaft, rocker arms and so on as the original short block Lots of discussion on this topic, every builder and keyboard expert has there own idea on this, you heard mine If the block you have needs help buy a better block Don't patch it with fill BTW, one of the 426 hemi blocks I did fill at the owner insistance pushed a freeze plug out part way, I ended up replacing that freeze plug it after dyno testing it, I found out that the water was seeping down between the block and the cement, same thing on the cylinder walls, the cement shrunk after curing Why reduce the amount of coolant and contact surface by filling it with filler