The July 2019 issue of Hemmings' Muscle Machines magazine had an interesting article about the 426 Street Hemi's true horsepower. Officially, it was rated at 425 hp.@5,000 rpm. However, just like the high-revving 340 engine that was under-rated at 275 hp.@5,000, the Hemi did not make its peak horsepower until 6,000 rpm. The article cites a freshly built 1966 Street Hemi that cranked out 459 hp.@5,000 rpm and 494 hp. at 5,900 rpm with stock exhaust manifolds and no air cleaner. The engine had solid lifters, an electric water pump, electronic ignition and a .25 increase in compression. In a dyno test of another correctly restored Hemi, the engine made 425 hp.@5,000 rpm (the factory's advertised number) and 500 hp.@6,000 rpm.
Add a roller Crower Cam, bigger Carbs and a little Head Work And those things CAME ALIVE And I can attest to the 5-7k pull I still set the Shift Light at 5500 as it was my daily driver too. I really miss the sound