Today is April 26, or 426, which HOT ROD proclaims as 426 Hemi day! During the early 1960s, Dodge execs realized the heat had been turned up in NASCAR, and a new engine was needed to take the 1964 Daytona 500. Helmed by “Father of the Hemi” Tom Hoover, the 426 Hemi was dreamed up in late-1962, and the earliest castings were assembled into a final engine in January 1964. Initial testing, just weeks ahead of Daytona, showed several issues with blocks cracking. While engineers initially tried thickening the cylinder walls, they soon learned that internal stresses caused during the casting process were the culprit of the cracks. When engineers and metallurgists discovered this, they began annealing, or cooling the blocks internally and externally at an even pace, to relieve the internal stresses in the block. The rest, as they say, is history.