First, the Easy Rider was never dynoed, so any hp numbers would just be a guess. Next, Keith Thruxton was indeed the tuner, and he estimated the motors put out around 200 hp each on a big load of nitro, around 80% I believe. Dave Campos, a few years ago was here at the house for a cockpit fitting, and we talked about the Easy Rider liner at length. hp came up in the conversation and Dave had this to say. The rear engine on every run was doing most of the work. The front engine, which had a 5 degree lead, to keep the HYVO from going south, never made the hp the rear engine made. It just didn't make the heat as the rear engine did. At one time they even contemplated disconnecting the water cooled jackets on the cylinders to get some heat in the motor. Anyway, from the horses mouth, the two engines never made over 350 hp. That was enough to go the 322+ mph. The liner was pretty aerodynamic, and the big bang on nitro provided the torque to get the job done.
It doesn't take a lot of hp to go fast if you have the aerodynamics and traction. Don Vesco went over 300 mph on two gas burning Yamaha motors, making 80 hp each, and he told me these were the only engines that he ever dynoed on any of his salt racing vehicles, both cars and motorcycles.
