Historic. Legendary. Unbeatable. These—and many other descriptive words have been used to describe the 426 Hemi since its public introduction in 1964, but how did we get there?
It was December of 1962 when Lynn Townsend set the wheels in motion by authorizing the build of a new engine for the sole purpose of being a race-ready engine that could go to the 1964 Daytona 500—and win. For Willem Weertman and his crew at Highland Park, they had no time to come up with a plan. What they initially proposed, was a radical head design that would fit the already popular 440 block. The head that they envisioned would have a hemispherical-chamber design, and valves directly across from each other that would increase the power potential of the 440 exponentially. It was soon learned that using the 440 block presented more problems that needed overcome in such a short time, and it was going to be easier to build an all-new block. In March of 1963, the task of designing the heads was complete, and by December of that year, all of the ancillary parts were also ready, and testing could be done. On January 28, 1964, the 426 Hemi (Project A-846), roared to life in the dyno cell of Chrysler, beginning tests on the engine for a debut at the 1964 Daytona 500, and we all know how that went.
During the dyno testing that was being done to simulate what the engine would experience during the 500 miles at Daytona, a few problems arose. For some reason, the cylinders began cracking. This presented a huge problem, because the Dodge and Plymouth race teams would be rolling into Daytona in one week.
Willem Weertman and Larry Adams—the man in charge of race engine development, figured that if they make the cylinder bores thicker, the problem would be solved. This added material in the casting, meant that the sand cores being used to make the block would have to be modified by hand. This modification permitted more of the molten iron to flow into the cylinder wall area, and thus create thicker-wall cylinder bores.
With that fix in play, along came another disaster. During this revised casting process, a severe porosity issue presented itself. It was learned that the issue was caused by too much residual moisture in the sand cores. This was an easy fix, and all that was needed was a more thorough baking the sand cores before they were used to make the blocks.
Another issue that reared its ugly head at this time was residual stress in the blocks caused by the actual casting process. Residual stress is a stress formation found in a solid material, after the original cause of the stressing occurrence (in this case, the casting process), had ended. Unintended residual stress in a designed structure may cause it to fail prematurely. The metallurgists back at Chrysler came up with a plan to relieve it by annealing the blocks after the casting process once they had cooled. Once the blocks were cast, they would go into a furnace and get heated to 1,200 degrees Fahrenheit, and then they were slowly allowed to cool, and this relieved the stresses in the block.
When the 1964 Daytona race was over, the 426 Hemi (coded A-864), had placed 1st, 2nd, 3rd, and 4th. The total Chrysler domination of the Daytona race caused the Ford and Chevrolet camps to get their panties in a bunch, so for 1965, the sanctioning body decided to change their production rules. The mandate required that Chrysler make the Hemi available in production cars in order to comply with NASCAR regulations. This created an unbelievably huge problem for Chrysler, since at the time, the engine was only built for racing. They didn't feel that the engine was marketable in a standard production vehicle. What this did, was make the Hemi ineligible for competition when the 1965 NASCAR season was starting. Chrysler was on the outside looking in.
The 1965 hiatus, would eventually give them the necessary time to come up with a street-ready version of the Hemi. During the process, they had to create something that would be more durable for the open market. While Chrysler was out of NASCAR for 1965, they didn't completely forget racing, they did however change their focus. This was the year that Chrysler produced a special run of cars that were limited in their production numbers. They were identified by the first digits of their VIN number. If you had a Plymouth, R0 started your VIN, and W0 was used for Dodge. The Hemi engine package was called A-990.
It was reported that Willem Weertman stated that 210 examples (coded A-990) would be built. This was to begin on November 16, 1964, and finish on January 8, 1965. Each of the engines for these cars was assembled by hand at Chrysler's Highland Park facility. The engine spent hundreds of hours on the dyno, as engineers worked at refining the package following the Daytona 500 introduction. That time also saw the creation and production of aluminum cylinder heads (with redesigned intake runners for better fuel flow), and an ultra-light magnesium intake manifold supporting two Holley carburetors. Compression for this animal was set at 12.5:1, and a set of heavy—but high-flowing exhaust manifolds, funneled back toward a single muffler behind the rear axle. The sole purpose of the exhaust was to say the car had a street-legal exhaust, but as soon as the cars were delivered, that was one of the first things to get removed.