They are but it works..the ramps are different...I've done it before with flat tappet hydros to solid flat tappets too. Gotta go with a heavier valve spring for the solids. did it to a 327 years ago hydro to flat and all the sudden I had a 327 that would rev easily to 7 grand. the lash will in effect lessen the duration and make the cam seem smaller but I didnt really notice a difference on the butt dyno other than the rpm increase. A local drag guy turned me on to it when I was just getting in to building motors.
