Hydraulic lifter cams have a different lobe profile, because the slow lift rate "acceleration ramp" that takes up the clearance on a hydraulic lifter shaft is very short- - - -like less than .005" instead of 10 or more like a solid lifter shaft. When hydraulics are run against a solid lifter cam, the effective result is a longer duration where the valve is open slightly, possibly creating a little idle roughness. It doesn't really enhance performance, but it does make the engine hard to tune. I recently degreed a new solid lifter cam ground for a 261 engine, and the acceleration ramps exactly matched the valve adjustment specifications provided by the cam grinder. You would need a degree wheel, a dial indicator, and some experience setting up racing engines to interpret the measurements you record to determine if you're actually running a solid lifter cam.
Putting solid lifters on a hydraulic cam is a disaster waiting to happen, as the lobes are not designed for solid lifter clearances and the engine will be noisy and the cam and lifters will wear out rapidly. Clearance would have to be run at about .005" or less on both intake and exhaust lobes, and the valves would have to be adjusted very often.
Jerry
