It depends, I have bought quite a few used steel roller cams, some injured and the some not . As far as a flat tappet cam(solid or hydrauylic) it would really depend if it was in the car and I could make sure the lifters where mark on te lobes they came off of and I got to measure the lobes of the cam for lift before buying it The second thing is to check the bottom of the lifters for wear marks, flat or ruined lifters and so on, probally best to not buy a used one of those on second thought